There has to be some way to register negative feedback so that you can find out what is widely unpopular. The key is to lower the power of individual down-votes so that an idea can’t be easily trashed to the point where most visitors won’t even consider reading it. (I find myself doing this sub-consciously in review sites and app stores for instance, where once something falls to about 3 stars I don’t even want to see what the fuss is about, I just skip it.)

One thing I’ve never seen is a vote that accounts for the number of unique visitors, or the total time that visitors spend on a page, or even contributor status, before weighing feedback. An issue that isn’t immediately important to a lot of people should require some time to decide popular/unpopular status.

A page shouldn’t show up/down status to anybody* until a significant amount of feedback has been collected, either. This would prevent knee-jerk down-votes of ideas that seem unpopular to everyone based on a few early down-voters. A proposal should stand on its own, at first. After a certain time period, the page could reveal whether or not an idea has really turned out to be popular, and at that point the cost of up-vote/down-vote could change (e.g. maybe only comments are allowed at that point, and no simple clicks).