I don't understand exactly what we mean by anonymous transaction.
If Alice and Bob want to trade some stuffs, what prevent them from using GnuPG to do both negociation and bitcoin address communication in an encrypted manner??
I know that Bob could be a police officer pretending he's just a customer, but still...
The problem is in the transfer of funds. Also, what you've described is a SECURE transaction, not an ANONYMOUS transaction. With bitcoin, you can transfer money to someone whom you have NO idea who they are (plausible deniability) etc.
