I think if you are really a serious crypto investors, putting your wallet.dat on cloud storage in the last thing you should do. Be creative, buy a solid commercialised safety box, or even get one in a back for you the safe keeping of you hardware backups.
Sooner or later hackers will find a way to exploit cloud system (if they haven't done so) so it's not really recommend to do it, in my opinion. Hackers are not just evolving, they are always two steps ahead on this game.
It's possible to encrypt your wallet in Bitcoin-Qt, but you shouldn't rely on that alone. You should add an additional layer of encryption with TrueCrypt, with a different password of course, so it will end up doubly encrypted. And if you are paranoid, use 7-Zip and GPG (symmetric) over the file and put it in SpiderOak/Tresorit/any other online encrypted storage. This way, when one of encryption tools and/or algorithms gets compromised, your Bitcoins are still safe. Sure, that's 5 passwords to remember, but it's not impossible.
And I didn't say about storing your wallet copies in the tool, I just told about storing copies of PaperBack program in your cloud account.