Should poll questions be Community Wiki?
In other words, should they count for reputation for the question asker?
Yes, because a poll question effectively belongs to the community, in my opinion. If the question author is not looking for an answer to a specific problem of theirs, but is simply compiling a list of something that may be useful to others in the community, then the community should have more control over how it is formatted and edited. Making it a Community Wiki thus allows more people in the community to control the content (due to the lower Rep threshold for editing).
In principle, there's no reason why they should be. Either the question is off-topic and should be removed, or it's on-topic and its wiki state should be at the discretion of its author.
In practice, there's a very good reason why they should be: polls work very, very poorly when answers cannot be voted on without giving or taking rep from the voters and votees. Furthermore, when posting a popular answer stands to garner rep for its author, there's more temptation to post a duplicate rather than up-voting an existing answer. And making a question CW is the only way to force all answers to be CW as well.
So long as the system continues to work this way, poll questions should always be CW for practical reasons. Admins should force this upon them if the original author neglects to do so...
On Stack Overflow, Server Fault, and Super User, yes, but this is more because polls are subjective in nature, and subjective questions on the big 3 are either marked as CW or closed to prevent inordinate reputation gain.
Here on Meta, no. Meta is, by design, a site that deals with subjective questions and discussion all the time, and it makes no sense to force all of it into Community Wiki. In fact, back when Meta was initially created, I was in favor of the elimination of Wiki completely from the site.
However, since the migration of the FAQ over here, I've come to recognize the need for the "Wiki" aspect of "Community Wiki". Also, when conducting a poll, it's important to mark the responses as "Community Wiki" so people can vote them down without losing rep.
However, apart from the slight convenience in forcing all the answers into CW, there's no reason why the poll question itself has to be CW here on Meta.
Couldn't we make a new kind of question, similar to community wiki but call it a poll?
For example: This question asks Is it always evil to have a struct with methods? This question is about best practice and is subjective.
Clearly a "normal type question" is not not suitable since it is unfair to decrese users reputation based on their answers to subjective answers.
I also don't think that it should be a "community wiki" because that invites editing of the entire post (as opposed to just formatting etc).
I think that a new type of question should be created called a poll, for subjective questions.
(It seems especially useful for meta. In fact I think that this question should be a poll.)