>The system is working exactly how it is supposed to.

US system is designed to be anti-markets and pro business, so you have a point. Good for startup, good for FB, bad for consumer and competition.

It's still against what anti-trust law was supposed to be.

Also remember that in the US it's perfectly legal to be a monopoly. What is illegal is abusing your monopoly position by engaging in unfair practices (which is a rather fuzzy and hard-to-prove thing).