I haven't collected any action figures before, after I spent my childhood with Masters, Star Wars, MASK, GI Joe, etc. I was clean for over a decade and then I stumbled upon a pic in the internet, showing a tiny LEGO man looking just like Captain America who happened to be able to strap his shield on his back. Frack me, the desire for that guy struck me from nowhere. Of course I figured out that you couldn't buy this guy here in Germany. Anyway. A little research later, I found out about Minimates and picked up the Invaders set off of eBay. (Newbie, I know.) And damn, that guy rocked. The details were amazing, the interchangable parts just great and the articulation superb. I only needed that one little figure...
Then I stumbled upon this forum. Learned about customizing, which I actually never thought about before, since I haven't bought any figure for ages. Customs got me seriously hooked. The possibilities are incredible. I was able to have all figures from every minor story/movie/comic/cartoon I wanted. Just great.
So I usually collect characters that I like from all different lines and figures that offer a high potential for customization.
But, as some have already mentioned before, without this community, I wouldn't have stayed as long as I did so far.