I no longer think it is community friendly behavior to cast an extreme number of downvotes, and I am considering an explicit policy forbidding it.
Are you trying to make people act friendly by changing policy? On the face of it, that doesn't sound like a good idea at all.
The world is not a carebear world, and even though I want the SO environment to be more welcoming than the real world, I don't see legislating downvotes changing that. The main sources of unfriendliness are, IMHO, comments, answers, and other actions, rather than downvotes.
I've noticed more downvoting on my part recently. I went from somewhere around 1,700:600 (2.83:1) to my present 1,893:1,110 (1.71:1) for about 200:500 (0.40:1) in my most recent votes. According to those numbers, approx. my last month's worth of voting doesn't meet the suggested 'friendliness requirement'. Yet, I don't feel like I'm doing anything wrong. Am I blind and hateful?
It's not a conscious decision, but I have run into the daily vote limit often. Perhaps I have subconsciously realized I only have 30 votes per day and that upvoting from 5 to 6 isn't nearly as useful as legitimately downvoting from 2 to 1 or 0 to -1? It's not that I don't want to upvote; I'm trying to make the most positive impact possible (legitimately pointing out errors and flaws should be a positive improvement, right?) and have limited votes to do it with.
 Speaking of which, I bookmark posts when that happens, is my rapid-fire voting the next day on all those saved bookmarks triggering any "suspicious voting"?
 I am happy to reverse the vote when they respond to my comment and point out where I'm wrong, or fix the flaw, etc. Or, as pointed out elsewhere here, if they just delete then they can get the rep back in a recalc, but the downvote stays on my record.
To temper that 200:500 ratio, I realized that a large chunk of those downvotes (about 100? strongly doubt it's more) are from community wiki questions, where I downvoted to express opinion, indicate duplicates (e.g. on the questions with 75+ answers), and so forth. I have more "large" CW questions bookmarked, and could easily add 30 downvotes/day for several days by just going through most of them (again, upvoting good answers on those questions is largely redundant at this point, and I'd rather point out duplicates and flaws).
In reference to dmckee's comment regarding downvotes being appropriate: In a rep recalc (completed recently, and the first my account has ever had, AFAIK), I gained ~100 rep but didn't see a decrease in my downvote count. However, I also know I have one deleted answer with +6 votes, plus misc. others, so could it have been up to ~200 downvotes on now deleted non-CW questions/answers? I have extremely few, if any, downvoted and deleted answers (e.g. no peer pressure badge).
Taking the higher estimate of 200 downvotes (but please someone mention if I've misinterpreted), that means roughly 18% of my downvotes have been explicitly endorsed by either the original poster or the high-rep users (i.e. owner-deleted answer or closed+deleted question+answers), which seems like a decent percentage.