Bitcoin is traceable by nature. Anyone who makes claims of anonymity either doesn't understand how it works or has a system in place that provides uncertainty (ie tumbling).
People seem to think that coins are 'clean' after tumbling, but I think its much more likely that you'll get back more suspicious coins: superlatively, "Here's my personal-use drug bitcoin, give me coins that were earned by assassinating someone"
If I were a narcotics undercover agent, I'd be working to become The Guy locally to trade Bitcoins with in this manner.
Have a partner snap a photo or follow them home to compile a list of people transacting like this.
Chances are good this is already happening in some cities.
And if your id is leaked in one transaction, it links your id to all other transactions done with that wallet.