They are frequently down momentarily. Don't be alarmed. Just wait a bit and they are usually back up in 15 minutes. If you are worried about your wallet, do a backup of your keys from time to time.
No, I'm not worried about my wallet... of course I have a backup and I only keep a small amount on blockchain anyway.
My point is that the lack of reliability deters new users from adopting bitcoin. Case in point, the site is down again today.
For widespread adoption, an easy to use and reliable platform has to exist. For now, blockchain.info does not seem to be up to the task.