I use Github, and I love it, but they're closed-source, in spite of so many free software projects being hosted on the site itself. It's ironic. Now, of course, Github doesn't have vendor lock-in because it runs on Git, and you can switch to Gitorious should you need to, but nobody will be there, and there's no features. In essence, you either use Github and it's awesome yet closed-source interface, or you just do local revision control or use a hosting site nobody uses.
It's a vicious cycle. What if Github changes something? We can't change it back. What if they implement a backdoor to leak code out to third-parties? We can't change it back. We can't move anywhere else either, because everyone uses Github.
You can apply this scenario to perhaps more critical applications as well. Office is one more example.