I've had the thugs with the contract attack me twice, both sent by people who I stole from but didn't catch me at the time. I assume that since I was the only other person in their shop and I was the one who put the cauldron on their head right before all their stuff went missing they just /assumed/ it was me. >:(
I also had the random DB assassin attack me once, right after I started fighting a dragon. :(( Didn't seem to lead anywhere, although haven't joined the DB with any character yet.