vTXOs in a shared UTXO are self-isolated from each other. One vTXO exiting tree doesn't affect the others.

brqgoo

This wouldn't be a DDOS attack. Everyone else's vtxo is locked into the sharedUTXO which is being paid to the ASP until the 4 week timeout. 

When the remaining members of the shared UTXO come back online at the 4 week mark, the ASP pushes them into the next coinjoin round to create another sharedUTXO with other people who are entering in that round.

ecurrencyhodler

Does a single user's unilateral exit force everyone in their VTXO set (meaning all users of the ASP who made a payment in that 5 second interval) to chain?   If so this could be a type of DoS attack.  The single attacker pays an onchain fee, now thousands or tens of thousands of people have to also.  Maybe miners even profit from this attack?  Pay a single fee and send thousands of fees to miners?