The best thing to have happened to the Internet is Yahoo being priced out of acquiring Google and Facebook during their early stages. Its pretty clear what would have been made of them under Yahoo's roof.
I think the majority of these companies suck at so much because they try and be all things to all people. In unity there is strength, but when you try to do it all, you fail.
I don't trust Google because they have their fingers in every pie on the Internet. They want to make money, money, money with little thought of anything else or what it takes to get there or how much privacy is looted. Yahoo is an also ran with little hope of being anything more than what it was and is.
OTOH Facebook being so dominant has no positive effects that I'm aware of. Hurting Facebook creates a win for everyone across the board. As upsetting as it is, they really do seem to be passed the size where they can quickly fall apart (like MySpace).
On a slightly related note, I'm also bewildered how MS could have considered dozens of billions for Yahoo, but let Sun get bought by Oracle for so little.