It's also worth pointing out that it doesn't have to come from malicious intentions.
It's replacing an open, free (in both senses), decentralized system with a closed, for-profit, centralized one that expressly benefits a single organization at the expense of everyone else in the ecosystem.
This is not to say that GitHub isn't a benefit over emailing patches around; just that it's probably also worth mentioning that Linus et al have not migrated to this shiny new (centralized) system for the largest collaborative development effort in the history of the world, and, indeed, git itself was developed specifically to avoid a hard dependency on a single, centralized point.
Also, FWIW I think we need to move away from GitHub.