But still, I just started using Firebase, and this news makes it clear to me that I should move off them as soon as I can. Firebase was an interesting technology supplier: When they were a small company, I could count on it that as a customer, I would count. Google is known to not give a damn about paying customers (ref: all the Google Apps customers who lose their email (for whatever reason) and get redirected to a FAQ page with answers to unrelated questions). Google is also known to Be Evil: I'm not sure I dare waiting until the terms change such that my user's data is subject to googlebot scanning.
Firebase's business model is aligned with my interests: the more users I have, the more I (hopefully) earn, so the more I pay Firebase. I strongly doubt, however, that Google is buying Firebase because they think they can get very rich selling Firebase subscriptions. It's either going to turn out a acquihire, or it is some part of a grand ecosystem plan. Acquihire means they'll pull the plug sooner or later, grand ecosystem plan means vendor lock-in. While I'm happy to be locked in to the services of a small independent business, I'd think twice before becoming entirely dependent on a company that could lose me as a customer and not even notice the slightest impact on their bottom line.
I know all of the Firebase guys are reading this, and I don't mean to piss on your parade. I'm certain you're not lying when you say that things are only going to get better. But I'm also certain that your jobs don't depend on that anymore, and when higher-ups decide to move the big boat's direction, Firebase might be over sooner than any of us wants it to.
That's a pretty big risk to take as a startup that fully depends on Firebase for their data storage.