> Why? If they federate, I can follow people who post on Threads, but I get a chronological timeline I control and no ads. They make money on ads. So why should they federate? To "slurp up everything"? They already have much more than Mastodon and the rest of the fediverse have.
The thing you get from federation is more granular social graph data than you can obtain from public scraping. Not just "X liked this post" but also "when did X like this post?"
Meta specializes in social graph analysis. More data leads to more insights, which leads to more targeting for advertisements in places they do control. There's the direct profitability angle.
Additionally, it will make Meta's properties feel more "complete" or connected to the rest of the world (despite many people's distaste for Meta as a company and their business practices). Being able to stay in touch with Meta objectors through ActivityPub will lead to more social pressure (or inertia, depending on your perspective) to stay locked into Meta properties for their incumbent users.
They only stand to gain from this plan. There is a cost, of course: Some CPU is expended that doesn't include adverts. But they've probably done the math and concluded that they can accept that hit and still profit.