My guess, and IANAL, is that it would hold in many courts, but not in Californian ones. California seems to have little tolerance for contracts that restrict basic freedoms (e.g., non-compete agreements.) In this case the basic freedom is to be compensated according to the tort perpetrated, and not limited to a specified arbitrary amount.

My understanding is that these contract terms have teeth in California, just like everywhere else. An enforceable contract doesn't mean you can't sue Dropbox if they cough up your data to an attacker; it just means you sue for a tort instead of breach-of-contract.