My guess is that this will end up the same was as the Microsoft case. Building network effects is not anti-competitive behavior. FB will argue that they are in

My guess is that this will end up the same was as the Microsoft case. Building network effects is not anti-competitive behavior. FB will argue that they are in fierce competition with Google in the market where they make their revenue, advertising. Not really relevant what the relative market concentration is in other non-revenue generating markets (social networking / search), which are only used to generate attention for the ads they sell in a market where FB's relative market power is < 50%.