I think in B2C markets, its definitely a fear. Witness how many people use Gmail because its free. But B2B products? I'd have no fear of Google coming into my market. I'd be more worried if it was Amazon, Apple, or Facebook to a lesser extent.
Be fair, I started using Gmail all those years ago because it was awesome. And although it's stagnated and they're about to fuck up the desktop UI by "Materializing" it, it's still pretty good.
