I did some work (non-IT) for a retired internet billionaire, who doesn't mind one bit using gmail as his private email address even though Google is a direct competitor to the company he got rich with (and they have the upper hand in their market).

Likewise, one of his start-ups' (1 million unique visitors per day) entire closed-source code base is on Github.

From a legal and commercial point of view, it would be devastating to Google et al. if they were found to be stealing IP like that.