Wallets are only as safe as you are. Blockchain.info is very safe providing you set up all the security features. Make sure you have 2-factor authentication set up at a minimum.
Strange to see a global moderator advising this. anything which comes into contact with online properties is vunerable. the way blockchain.info works its vunerable to rnb and man in the middle attacks and possibly a hostile take down which would mean people losing access to their private keys unless they export them which in itself means its being broadcasted to client side which effectivly opens it up for exploits although it is encryped of course