In my experience, question popularity has a lot to do with what time-of-day it's asked. Also, I suspect that the day of the week is important too. These are just suppositions, however. Does time of day and day of the week in which a question is asked affect its popularity? If so, when and how?
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Jeff posted stats here on the blog awhile ago. I also know he's said, if not posted data related to the fact that weekends see significantly less data than M-F.
As to whether this affects popularity, I believe it certainly does. While there is skill is asking a good question (clearly stating the problem, etc), there is definitely an amount of luck to getting a question that turns out to be popular. Especially on the weekends it seems that questions can kind of go relatively unseen, regardless of how good of a question it is/was.
It affects it in just the most obvious ways, as in when more people are online you're more likely to get answers. Usually weekdays are much more active than weekends. As for the time of day, here's a good graph to illustrate the peak times.