It is definitely concerning. 10 years ago I wasn't worried about putting my data in things like Dropbox because the general fear was "what if they go out of business?" to which I felt reasonably secure that I'd have time to get my data out of there before they shut down for good.

Now, it's much more likely that you'll get a "You have violated our Terms of Service and are banned from using <the service>", pointing you to a line that looks like: "The company may, at its sole discretion, decide what constitutes a violation of the Terms of Service, and terminate services as a result." It happens!