You're right about google's track record but at heart yours is a comment about third-party cloud dependency, not google. As you mention, offline storage solves this and another commenter mentioned msft will ban you also (but you dont hear about it because...offline storage)
Track record is a factor that you should consider.
When companies buy services from others they often ensure that the contract has protection from things like this. They have clauses that the data belongs to them. They have clauses about what happens if the company is sold. They have clauses about abandoning the product. They have a number of other things added that I'm not aware of.
You as a single individual (and often as a small business) don't have the power to get that into a contract. However you still should read the fine print - you should go elsewhere if it the fine print is against you.
