re: Anti-trust laws have been used for AT&T, MS, Std Oil. Why not Google, Facebook, etc.?

Anti-trust is a really fascinating subject, but a short answer to your question: a lot of times it won't come into play when the player at hand gained market share through what is essentially organic growth. In other words, the Googles and Facebooks of the world were revolutionary enough that they brought such immense value to the customer that the "cost" side didn't really matter.

Anti-trust really starts to come into play when you get into M&A (see: Cigna/Anthem or Staples/Office Depot) or outright anti-competitive maneuvers (what, as I recall, Standard was doing, though I am not super-familiar with the business case there). It could be argued that Facebook's acquisition of Instagram was an example, but that's really tough to do considering both services are free to the consumer. A lot of tech companies haven't hit that threshold yet (except Microsoft) because the what they're doing is so new. You have to define the market first before determining anti-trust/anti-competitive maneuvers.

It will be interesting to see what eventually happens because, just like in the Gilded Age (trains, logistics, petroleum, etc.), there are a hell of a lot of demand-side economies of scale (network effects) involved, and the big boys eventually tipped the scales and started doing all sorts of anti-competitive things. Amazon, arguably, might be doing some of that right now, but I don't know if Facebook and Google have approached that threshold yet.