We're not enemies. We're not competing. We're trying to make developers lives better, and there are a number of techniques that can work, and a number of tools that can help them.
Edit: sarcasm aside, you're right in saying that there is competition here. And competition is healthy, it's what drives us to solve problems in different ways and _allows_ us to collaborate. But to suggest that we shouldn't use each others technologies feels short sighted and like the wrong kind of competition.
You have to be careful what you use other technology for. If you don't show that you're relying on your own product when you clearly have a chance to do so, you immediately lose trust. First impressions matter a ton there.
SCM hosting is very different than SCM software; the latter is usually... not lucrative.
Eg; I'm sure MSFT hopes to make money from their GVFS effort, but not by selling it – simply by using it as a marketing tool to establish credibility (eg; for Team Foundation Server and other developer products).
Even if nobody _used_ GVFS, it could still be a profitable project for MSFT if it made everyone think MSFT an expert in source control. (To be clear, I love this incentive structure, and it's working on me – my respect for Microsoft is growing, thanks in part to GVFS).