I wouldn't mind -- strictly from a user standpoint -- if all code was in one place. It's easier to collaborate and contribute to other repositories when they're all in the same SCM and host. If someone has their source in another host (whether it's Git or some other SCM), I'm less likely to bother contributing -- and I would assume this is the case with many others.

Of course, from an "all your eggs in one basket" or business monopolization standpoint, I agree with the author.

But selfishly speaking, I like Github and find that it adds more value to me the more it becomes a monoculture.