Is there any risk associated with using the same passphrase on two different wallets both hosted on blockchain.info? Does blockchain.info use any salt with the passphrase?

I.e., is there any risk associated with using the same passphrase on two different wallets both hosted on blockchain.info?

edit: of course blockchain.info doesn't even keep the hash of the passphrase, as opposite to traditional login systems, so it might not make sense to use a salt in the first place... or does it?
The risk is that, if a hacker gets a hold of one, then they've gotten a hold of both. Or at least If I had one passphrase, it would be my first guess for the second. 

However I dont think there is any inherent technical problem for blockchain.info.