Consider the account of yahoo (for example mate). If he needs a loan and he offers his account as collateral then anyone will accept it coz they knows yahoo values his account. He will do anything to take his account back. Now what if he don't pay back and default the loan. You go and tag the lender if he wants to sell it and also tag yahoo's account because it will be bought account?
At a minimum I would expect users in the DT network to tag my account if it is in fact a sold account in your hypothetical example here. My account, if bought, could most definitely be used to scam a large amount of bitcoin.
I am not attacking anyone here personally either, just joking with The Pharmacist in my 1st post, but I am very curious to see where this discussion leads so that current and potential DT users have something to reference when these sorts of situations arise.