The net impact of these companies is massively positive. Facebook, with its trust-engendering social graph, enables huge numbers of businesses and social groups to exist that otherwise couldn't while Google has enabled so much information discovery that we just take for granted now.

Of course I would argue there's a better way to provide these kinds of services that concentrates power less, and that's decentralization with cryptoeconomic incentives to maintain consensus, but for their generation, they did well.