[sneak]

Then they get investigated, then give the investigators your contact info that they used to transact with you.

[hexonexxon]

Oh noes, then they get a Tor exit node where you contacted them on IRC or Bitcointalk forums, or a JonDonym free proxy you will never use again

[sneak]

It's also hard to get any significant amount of bitcoins anonymously in the first place to begin this process.