With careful precautions, Bitcoin can, I'm sure, be used anonymously. (Mine the coins yourself, connect to the network using TOR, never use your computer for anything else, be paranoid, never pay for a transaction that could be linked to you, etc).
By this argument, credit cards can be used anonymously too. But everyone isn't going around saying that credit cards are anonymous.
If, sometime in future, Bitcoin happened to be commonly used for online commerce, by casual, semi technical users, then, with the system as its currently implemented in clients, most of most peoples transactions are going to be very obviously linked to other transactions that are linked to their real identities.
If, as the implementation currently stands, casual users were doing their Amazon.com shopping using Bitcoin, Bitcoin probably wouldn't look very anonymous to Amazon at all.
I can only guess how anonymous it looks to Mt Gox.