Ok, thought just occurred to me (I've been insanely preoccupied with studying for exams the past few days, so it hasn't exactly been the top thing on my mind). I wish to make a correction on my take-back of the extreme sports analogy... I'm so brain dead right now, so bear with me...

People may not SI to thrill-seek, per se. But it is similar to extreme sports in the sense that.... well, why do people who "live life on the edge", those adrenaline junkies, if you will, seek that thrill in the first place? To get a rush? To feel alive? Do we sometimes not SI for the same reasons? I mean, there are a number of reasons to SI: to express inner pain, to distract from pain... When we feel completely numb, we may SI just to FEEL. Feel pain. Feel alive. Feel SOMETHING. In this sense, it is similar to those extreme sporting adrenaline junkies/thrill-seekers. That's all I meant by that, lol. (Again, I am SO brain dead, so forgive the delayed elaboration of my analogy...)