GitHub IS very convenient. But it is a single point of failure or potential abuse.
I keep public projects there, but I wouldn't NOT also keep private repositories in sync with it on my own machines.
Also, I think it's dangerous to let GitHub become the official "address" of your project. Have a separate home-page / blog that you control that's the official home page, news of your project. That way, if you need to leave GitHub (either because it goes down or suddenly their terms of service become onerous) you can quickly update the page you own with a link to a new public repository.
Git itself was designed to be flexible enough that you can even use it over email so git itself doesn't become a bottleneck.
Phil