The FB shares aren't voting shares or are extremely diluted voting shares? This is the same scam Google and UPS pulled. Beware of owning second class stock shares. It means that someday the insiders can wave a magic wand and screw you over. Do you trust them? Maybe. But it doesn't mean they can't do what they want and "share holders" can't do a thing about it.
They're diluted, or his are inflated, however you want to look at it. Yes, it's similar to the Google structure, but Google isn't the prototype. Lots of companies over the years have had special shares with extra voting power, families often retain voting control of a company long after they've sold off most of the equity.
I'm always divided on this as a shareholder, but more often than not I do trust the founders more than the open market, yes. They have an emotional stake in the company that goes beyond short-term economic interests, and I've seen enough companies flounder after the market jettisons the people who built it, and enough recoveries when the founders return, to question the wisdom of shareholder power.
You speak of "going public" as if it's somehow turning over power to the general public. It's not. It's a colloquial term for a series of regulatory steps required to permit non-accredited investors to invest in a business. These steps are primarily designed not to exercise control over the operations of the company or its ownership and power structures, but to ensure a certain level of disclosure to investors whose resources and influence are limited.
There is nothing about going public that implies a general relinquishment of control of the company, nor is there anything about going public that mandates a particular ownership or power structure. Companies have "gone public" by selling only a few percent of their stock. Split voting rights are very common. None of this is even remotely illegal or unethical so long as it is disclosed, as it has been here.
If you do not like a company's control structure, you do not have to invest in it, whether the company is "public" or "private". As a shareholder, your relationship to the company is the same whether it's public or private.