Microsoft has a history of being hostile to the open-source and free-software communities. They release "shared source" code under licenses with onerous terms or encumbered with patents. In the event that an open-source project built on their technology becomes popular, Microsoft attempts to smother it (for example, see their treatment of Mono).
I trust Google about as much as I trust Red Hat, Canonical, or any other company with a history of friendly interaction with the community. While I'm certainly not going to give them my SSH keys, it seems reasonable to take advantage of open-source software that they release.