Is begging for upvotes looked down upon in the SO/SE community?
Yes. I would certainly hope so.
Votes are earned by providing technically correct and valid answers, or asking well thought out questions. It shows how much the community trusts you. Except on meta. Here sarcasm normally gains the upper hand.
Respect is earned, not asked for.
Short discussion and answer
“This site is all about getting answers. It's not a discussion forum. There's no chit-chat. Our goal is to have the best answers to every question, so if you see questions or answers that can be improved, you can edit them.”
If one can take an action that:
helps users get answers, in shorter time, with better results, etc. (“Ask questions, get answers, no distractions”),
follows other basic guidelines (see e.g. What kind of behavior is expected of users?: “Be honest, Be nice, Do not use signature, taglines, or greetings, Avoid overt self-promotion”),
then I guess one should take it, for the benefit of the community. Not taking it will likely lead to users having a lesser benefit than possible. A core component of SO’s system in place for objective 1 is vote counting and accepting.
(EDIT) I wonder why some find annoying that others try to help the community by a reminder for an upvote in any case without distinction. Moreover, I wonder why they find it more annoying than a comparable reminder for accepting an answer, or even than editing answers or questions. The three look very similar to me (this is probably worth another question), with the exception that editing is moderated. The interest behind any of these three may be reputation with helping as a side effect, or helping with reputation as a side effect. And in any case with or without technical merit.
I wouldn’t dare judging intentions, in general, and in particular if the outcome is useful for the community, and the inquiry is respectful. Some of these actions may not even fit the definition of rep-whoring: Stack Overflow users who post questions or answers for the sole benefit of accumulating as many reputation points as possible, without regard to the technical merit or the contribution to the system.
So, reminders for upvotes should not be looked down upon from the outset. Each case deserves specific attention.
PS: I do not know what is understood by "Begging for votes", and if it includes all cases of "Reminding for upvotes" (this is never specified).
A more detailed discussion.
Examples of actions encompassed by points 1, 2 above are:
Reminding askers “Ask about... Specific programming problems, Software algorithms, Coding techniques, Software development tools”, “Don't ask about... Questions you haven't tried to find an answer for (show your work!), Product or service recommendations or comparisons, Requests for lists of things, polls, opinions, discussions, etc., Anything not directly related to writing computer programs”. Most will agree that such reminders help improving usability of Stack Overflow.
Editing questions and answers. Idem.
Posting answers, even if they are short, as answers (instead of as comments, “Use comments to ask for more information or clarify a question or answer.”). There are quite a few interesting posts about this, which can be reached by searching “post answers as comments”. I do not mean to enter this discussion.
Posting a late, very detailed, answer. I am just supporting the heading, as I have personally benefited from such answers. I am not endorsing any of the statements in the post, though. Noteworthy: “If you are here for the rep,... But if you are here to help,...”. There are different possibilities.
Posting someone else’s comment as answer, possibly with some enhancements. Fragment “A question has been asked, an answer has been provided, and if your only contribution is to move the correct answer to the appropriate channel, it is no less a valuable contribution.” is worth noting.
Answering own questions. This was also very much discussed. I want to remark “If it's helpful to at least one other developer, it should be here.”.
Reminding an OP to accept an answer, when there are obvious indications that an answer should be qualified so (e.g., commented with “It worked exactly as intended”). Statements in a post dealing with new users for the most part agree, with some reservations (this is a subjective statement). A more generic question that does not focus on new users was marked as Possible Duplicate of the one above (I think it’s not, due to New User as OP vs. Any User as OP). It also included in the same question both “upvote/accept”. Within the very small sampling of voting, “Yes. Go ahead if you see that the question owner says it helped” took the lead. There are quite a few related posts and answers.
Reminding an OP to upvote an answer, when there are obvious indications that “This answer was useful” (the tooltip when hovering the arrow), and it is very likely that the OP did not do so. For instance, an answer commented with “It worked exactly as intended”, and with zero upvotes. It is clear that this may come from a balance up-down=0. Likeliness that the OP did not upvote is subjective, but if the OP already upvoted he/she will simply ignore the reminder (can´t do otherwise, anyway). This applies regardless of the poster of the reminder being the answerer or not. I was myself tempted to post reminders for someone else’s answers in a couple of very obvious cases some time ago (and I admit to not doing it... if I ever find those questions again I will likely post reminders). This also applies regardless of the answer being accepted or not.
Now, about example 9 (this pertains to example 8 as well).
It seems that quite a few people find annoying an action of type 9, much more than any of the others, and in particular more than type 8, or type 5. I guess that the feeling of annoyance might be based on the (possibly unconscious) perception that the poster of the reminder may be hunting for reputation (rep-whoring). Actually, the poster may or may not be (see example 4). Reputation increase may be the carrot in the stick, or a side effect.
What If the poster is politely rep-whoring? How can one know? (I quote “There is a thin line between being helpful to new users and being a rep whore. So tread lightly.” as interesting; not that I endorse it). I guess this point is not even relevant, if conditions 1 and 2 at the top are satisfied. If so, I would not find the comment annoying, but constructive. I wouldn’t even bother digressing into it.
I think that condition 1 is met here, as the reminder will likely help setting a rating according to actual usefulness, and thus help other readers to pinpoint more easily suitable answers. Condition 2 may or may not be met, depending on the request. If it is not met (possible example: “Hey, why didn’t you upvote?”; I find this a good reason for annoyance), it should be handled in some way, e.g., by flagging. That should train the poster.
Some may argue that if a comment is somewhat annoying, that is per se a violation of condition 2. My take is that this is a consequence of the suspicion of ignoble intentions. If so, I think one should get over it, for a greater common benefit. I will not dig any deeper into the logic of the situation.
Conclusion: I think that it is not just ok (i.e., we can live with that) to post reminders of types 8 or 9, but that it is advisable to do so (there exist suitable manners for doing it) since it helps bringing ratings to a more faithful representation of quality/usefulness. We all would spend less time, and on answers that are more relevant for our needs.
I guess this answer will capture quite a few downvotes, but in that case I would rather like to know what in the reasoning is not in line with Stack Overflow, instead of simply getting a downvote.