Unlike Coinbase and other services , Blockchain.info don't control our private keys and don't have our password stored in their servers but It's hackable , anyone with access to their servers could try to crack the wallet.dat and get some $$ in his hands with no effort as some passwords are weak.
I have one question could someone can also get hands in the bitcoins that was imported in blockchain.info if they crack wallet.dat file? And even getting access to wallet.dat file from blockchain.info server hacker will have hard time to crack individual wallet which they even don't know how much bitcoin it carry.
However it is true that no any web wallets should be considered as safe place to store bitcoins.