The problem is that Dropbox may, at their sole discretion, decide that providing ads is part of "the Service". Under their TOS, they could do that without chan

The problem is that Dropbox may, at their sole discretion, decide that providing ads is part of "the Service". Under their TOS, they could do that without changing it. Realistically, Dropbox won't ever do that. But the key thing here is that Dropbox's TOS does not explicitly state exactly what rights they believe they need to operate with.