1. Select a victim 2. Every time you are about to make a Bitcoin transaction, send an email to the victim's address requesting the amount you are about to send. (Bonus point if you can get directly into the spam folder.) 3. Send bitcoins as you intended to do.
Now lay back and wait for your victim to be linked to your shady activities.
(I'm writing this as a critique of the technique used and conclusions reached in the article. Hopefully the investigation has something more robust.)