Some guy lost 4 Bitcoins that were encrypted with a line from some obscure afrikaans poem, because someone was crazy enough to brute-force all possible private keys that you can come up with using basically any phrase you can find on the internet [0]. So as someone else already said - if it's online, it's not safe.

[0] http://www.reddit.com/r/Bitcoin/comments/1ptuf3/brain_wallet...