"Insecure Alias. Please login using your wallet identifier link."
I contacted them and they explained that they changed their policy, just a couple days ago, that aliases without an email attached will not work due to security concerns... I think it's an unnecessary move, and don't really see the logic.
Basically it is prevent automatic spidering of wallets using lists of usernames from other bitcoin sites or common english words.
If you have an email associated with your wallet if an unknown person tries to access it we can send you an email asking for your approval. Without an email we have no way to contact you, previously the default action was to allow login anyway now this has been changed to deny login.
You can still use blockchain.info with no contact information but must login using the identifier rather than an alias.
We need at least two of the following to find your wallet identifier
There is some confusion from the support staff here. If you are receiving this error simply send us your alias and we can send you the identifier without providing other information (If there is contact information associated with the wallet it must matches your own details).
"Application cache" tabs and under each one was a different guid (wallet identifier) i had used in the past.
This is the HTML 5 offline storage
http://www.html5rocks.com/en/tutorials/appcache/beginner/. It means you can still open your wallet even if blockchain.info is offline and is a good way you can recover your identifier without our help.