According to Orkut, Joi Ito can have only 1000 friends.

Ok, 64K it's enough for everybody..and so on. But, it's a though on real life compared to "online" life, is a limit of Orkut or is a limit of Social networks instead?

I think the last chance. It's a limit of social network implelementation and theory. Real life can't be simulated in all its various depects and aspects.