This is basically about the dilution and doesn’t specify Mark and Wardo’s relationship, it works whether you think of them as friends or lovers or anything in between. Personally, I think something definitely went down between the two at one point, but each to his own.
I think that Mark isn’t great at reading people, and so he didn’t really understand that Eduardo not coming out to California wasn’t Eduardo saying he didn’t care about Facebook. Mark was upset when Eduardo froze the account because he hadn’t realized to what extent he had upset Eduardo when he let Sean in. (Mark doesn’t seem like the kind of guy to talk about his feelings or have heart to hearts with Eduardo on a regular basis.) So when Mark drew up the contracts, he threw in a clause that meant he could dilute Eduardo out, not because he intended at that moment to cut Eduardo out, but noticing that clause would sting Eduardo in return for his freezing the account. Even more so, it was an instinct. Mark was being defensive and didn’t think things through. He didn’t consider the implications, or what would happen if Eduardo didn’t notice that one clause, because he was too caught up in his knee-jerk reaction. But then Eduardo signed the papers without noticing anything, and he continued to get upset about Sean and push for ads and tear Mark away from coding and just in general kept being Eduardo, and Mark didn’t know how to deal with his anger and annoyance, so he just tries to distance himself from Eduardo, because thats how he deals with these things like feelings — he avoids them, and it never really hits him that what he is doing is really, really hurting Eduardo. Part of him knows that he is part of the problem and that this is bad, but part of him also thinks that if Eduardo froze the account, he obviously didn’t care that much about the future of Facebook, and so it wouldn’t really matter if his shares got diluted. It wasn’t that Mark was an asshole, he just didn’t communicate well with Eduardo and didn’t know what to do about his feelings.