Pros
Mixi has a lot of money, and they often blur the lines between different jobs, so you can potentially make room for yourself and climb the ladder.
Cons
Japanese work culture. Mixi likes to say all kinds of nice things about itself, but once you actually start there, it's soon clear that it's not as nice you were told. Unpaid overtime for anything less than 40 hours, bosses angered if you go home when work ends and don't stay extra, blind trust between senior team members and management means you either fall in line with the rest or get an earful. "The nail that sticks out gets hammered down." People at Mixi, even the international staff, all have the same self-deprecating mindset. And if you're not like them, it's not going to work out for you.