Part of the movie's point is that Mark wanted to be accepted and "cool" so badly, that he was willing to do whatever it took in his own way to achieve that. Even at the expense of things most others wouldn't give for it, as you mentioned.

To many others, that social status is achievable in different ways -- athletics, personality, appearance, or is even inherited (name, money, etc.). So many, dare I say most, people joining the Finals Clubs don't have to make the kind of sacrifices Mark did because they just naturally fit in. And as a result, membership of those clubs is less of a "big deal" because they didn't have the mountain to climb to get in it.

In Mark's case, he didn't have any of the above to achieve that. But he found out he did have a really unique and "cool" way to socialize -- the social network. The popularity and notoriety from the things he did contributed to his "cool" status on campus. And as we all know, the money and power he got from it cemented his status as a "cool" kid with status.