Algorithmic gems in the data miner's cave

When I was younger and spent most of my time playing in the field of (more) theoretical computer science, I used to think of data mining as an uninteresting kind of game: I thought that area was a wild jungle of ad hoc techniques with no flesh to seek my teeth into. The truth is, I immediately become kind-of skeptical when I see a lot of money flying around: my communist nature pops out and I start seeing flaws everywhere. I was an idealist, back then, which is good. But in that specific case, I was simply wrong. You may say that I am trying to convince myself just because my soul has been sold already (and they didn’t even give me the thirty pieces of silver they promised, btw). Nonetheless, I will try to offer you evidences that there are some gems, out there in the data miner’s cave, that you yourself may appreciate. Who knows? Maybe you will decide to sell your soul to the devil too, after all.