I have been running my own home-based server for ages for my own personal code, and have tried one system or another (SVN, VSS, etc). But recently, I've enjoyed having some more precious (no source code) data off-site, without having to constantly worry about backups in case of hardware failure, using services like Dropbox, Skydrive, Google apps, etc.
This has made me want to do the same with my source code for various projects, however, I have a few worries about them. Namely, how secure is my code from curious/prying eyes, and do I need to possibly have a fail-safe service, in case one goes belly up overnight, or simply has massive data issues? This wasn't actually a concern until I read someone's experiences with Mozy.com, which while not a code repository service, data storage is data storage.
If you do use/recommend such a service, which would you recommend? I'm open to using any system, be it Mercurial, SVN, GIT, TFS, etc, so long as it has a Windows and a Mac client option (web-based would be a very nice "bonus"). And most importantly, why?