But he also tells me that Facebook "doesn't want to screw over developers" and says he's hopeful things will get back to normal soon.

When I met Federico Treu outside the San Jose Convention Centre, however, he is not as charitable.

Then again, his company Cubeyou has been suspended from Facebook over allegations of data misuse, and he is persona non grata at F8.

Mr Treu claims he has now proved to Facebook that the accusations against him are unfounded, but he is still angry and says his firm was thrown under the bus.

He also says Facebook is trying to divert attention from its own failings by blaming everyone else, including the Russians, developers and advertisers.

And he says the firm has a big job to do in restoring user trust. "I think the only way that is going to happen is through an external regulator."

Seeking reassurance

As well as getting users and developers back on side, Facebook may have to worry about some of its big corporate customers too.

Those are the kind of people social media consultant Sharon O'Dea has come to San Jose to represent.