They have every incentive to do the opposite though. Fake profiles still count towards ad-revenue because advertisers aren't calling Facebook out on their bullshit.
More to that I think some advertisers benefit from a known gullible community. It would be quite easy (and unethical) for someone to make money out of targeted ads piggybacking on this sort of network.
How? Unless the fake profiles manage to generate significant amount of ad fraud along the way, the advertisers still end up paying for actions, not impressions.
Why would an operator of a fraudulent network click on ads, sign up for third-party newsletters, install promoted mobile apps or do whatever else the dominant ad unit in his/her feed would promote?
You can't compete with mindshare on that scale. The network effects are ludicrous. People have made generally better products than Facebook for years that all wither because they don't have a billion people and everyone you already know on them.
If Facebook were using an open protocol like Ostatus anyone could make a peer network that is better than Facebook and actually compete, but their userbase is entirely locked into their platform. On purpose, of course, thats why investors value FB so highly. Its entirely against their interests to enable competition.
