I think some of it is the kind of comment it was as well. Negative public comments about specific employees are the kind of thing that would make a lot of people think the CEO was someone you should steer clear of, even if he weren't that high profile. If you saw it in a Tweet from a 10-person startup, it probably wouldn't make news, but it might be a red flag to potential employees. When you add to it that the guy is hugely wealthy, it just gives it an added aura of entitled-rich-asshole-looking-down-on-the-plebs.

Actually it reminds me of the kinds of reactions Sebastian Marshall gets around here for his jerky/arrogant/employee-badmouthing style of blogging, and that guy isn't even wealthy or famous (except HN-famous).