http://keepass.info/help/base/security.html#secencrypt
Hence, I am reasonably confident that even if Google were to turn over my Drive account to the NSA, they wouldn't be able to crack open the database.
See also: discussion on feasibility of brute forcing a KeePass database:
https://security.stackexchange.com/questions/8476/how-diffic...
And then the NSA is trying to crack it </tinfoil hat mode>
I've put my keepass file in the cloud for extra backup, and I know I can only rely on its cryptographic strength to keep it safe.
Google has no no way to know, if 10k people are storing their encrypted keepassx archives in gdrive, and if those 10k archives are accessed in rapid succession, that it's an attack. It's lost in the noise of gdrive traffic.