It’s not so much that they have a monopoly on anything but rather that they’re behaving in the way predatory monopolists do in order to dominate the market to the exclusion of competitors. For example, what’s being discussed in this action is their propensity to use the cash and power they’ve accumulated as the major player in the social search space to buy up any potential competitor before it gets too big (often paying a ridiculous premium to do so) and then either absorb it into their existing architecture or kill it. That’s anti-competitive behaviour in the interest of preserving an effective monopoly.
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