I also read that they were listed at random, but far too often I see the same products over and over again for my most popular tag. Then, I will get a ton of orders in little spurts and whenever I search for my most popular tag, I am on page 1. This has been happening for quite some time and I cannot for the life of me figure out their algorithm and I think they like it that way...
Laura, you bring up a very interesting point. I think you would be correct, it would certainly be an issue for someone creating unique items, however, if they are specific enough I would think that that tags/titles used, vs. what is being searched for wouldn't make much of a difference to that person.