Mixing service just makes it a bit ( may be very as of now  ) hard to trace the coins, but frankly speaking with bitcoin protocol I do not find it impossible to trace. The thing is that at the moment there is no real motivation for some one to write a tool to trace mixed coins transaction. If some one ( Government or any other thing ) wants it is possible to do that.

Bitcoin is not anonymous, at least as long as I see it

As far as normal money concerns, normal money is not easily traceable, the real advantage bitcoin gives is it allows you to store a good amount of wealth without need of much physical space. It is just like its much easy to hide it in black and dark than cash. But as far as trace ability  concerns, well,  bitcoin is much more convenient to trace than cash.

Cheers