Every now and then, an answer that got some upvotes when it was new and then nothing for days at a time will suddenly get a bunch of them in the course of a few minutes. I'm curious if that's a result of this algorithm that was mentioned on the podcast that puts old questions back on the default front page, or if there is some other social phenomenon in play? Anybody know?
As best as I can tell, people only tend to look at the top 5 or so answers. I've seen evidence of this in several ways. First, there's this way where you get several upvotes at once. Getting that first one may put you in the critical region at the top such that you get more people reading it and thus (hopefully) more people upvoting it.
The other way I've seen this play out is that a post will get an upvote and then a downvote relatively soon after. There hasn't been any edits or new answers so it hasn't been bumped. I believe it is often due to the same phenomenon: the first upvote makes it far more likely it'll be read.
Also don't forget that bumping isn't the only thing that'll attract attention to a post. It may get linked from elsewhere such that a bunch of people read it in a short time period. There was some post about integer square roots that attracted 13k views all of a sudden. Someone thought this was a bug but it had just made it to the front page of reddit.
IMO, the most likely reason is that you were linked from another recent question. A random blog link somewhere is also possible but less likely because the readers there may not have SO accounts.
There was a request earlier today to allow authors to somehow see referers.
One other possibility is that the Community user randomly bumped the question onto the front page. That leads to more views and thus votes for your answer.
This is possible even if you didn't see it getting bumped, because the front page may vary when people have favorited or ignored tags.