I tried out my MtGox YubiKey on the blockchain wallet service, and I noticed the OTP's that it generates are REUSABLE. It seems Blockchain.info is only looking at the first few letters of the OTP, as they are static, you can actually change the end of the OTP and the website will still accept it.

Doesn't sound secure at all to me and is definitely something that needs to be addressed. This is not 2-factor authentication.