You'll notice most engineering focused companies don't use Oracle because they decide on tech based on different criteria and allow more input from engineering and don't mind building things. They have to bet on tech or else they have no reason to exist.
eBay also used Oracle in the past (if you dig back in the past of their architecture/design of eBay).
Oracle SQL might be the fastest, most robust out of the box database, but for a huge deployment like Google/Facebook/Twitter, even out of the box Oracle SQL won't be good enough. It's kind of an unfair comparison.
That's not to say I'm defending Oracle's bullshit, but you gotta put these things in perspective.
[1] To be fair, I think this sort of thing permeates this type of "let's talk over lunch" sales model.