The problem with relying on a service like Google isn't so much the risk of them disappearing (though that does happen), but rather issues like:
* You accidentally delete the data. Poof. Gone.
* You forget some payments. Poof. Gone.
* You violate some ToS and they delete your account. Poof. Gone.
* They mistakenly *think* you violated some ToS and they delete your account. Poof. Gone.