.

when an exchange kills a coin, it should follow a protocol:

suggestions:

• give enough time between announcement and death
• alert the users, preferably by email (not everyone is daytrading)
• a mailinglist that users can subscribe to might help, to be informed about important events
• cancel all open orders of that coin, put them back onto balance
• keep the balance reachable for a few more weeks, to allow for withdrawal

what else?

Poloniex - Kills off coins every other day it seems. Some that still have active communities and development.
Mintpal - Promised to kill off coins, only one  I know of is Cagecoin
Cryptsy - Doesnt kill off coins, lets zombie coins like Royalcoin continue trade.

Good suggestions but exchanges are going to do whatever they feel like.

great but what if coin source code is bad? people will trade but noone will ever withdraw it?

VERY good suggestion.

And to make it simpler, a few defaults for recipient addresses in case of delisting:

• When I have deposited coins into the exchange, the sending address is stored (*)
• My last withdrawal address is always the one that would be used
• when I buy a new coin at an exchange, that coin is listed in my TODO list = I need to provide a fallback address

Only the last case really needs action from my side then.

(*) can cause problems if that was a mining pool, or another exchange.

It all starts when a Dev abandons his coin...
There needs to be a Posse that hunts down dead-beat Devs...
And brings them to justice.