How are bitcoins anonymous?

[Come-from-Beyond]

Please, elaborate.

When the government begins to pay close attention to all transactions and their originators, they will flood the Bitcoin network with a lot of their nodes (or a few nodes with thousands connections). If they control, say, 25% of all "connections", then they can determine the originator of a transaction with 90% success ( == 1 - 0.25^8 ). If they control 50%, then this chance will be 99.6%.

PS: They may already are doing this.

[gollum]

The only easy way bitcoin can be anonymous is to
-Always use TOR
-mine them yourself or in a pool
-spend them in a way that your real identity is not revealed