Why would they:
-Create witnesses that will do what negative actions exactly?
-Vote these witnesses in
-Prosper how so?
1. Short the coin
2. Vote in evil witnesses to halt the network, driving the price to 0
3. Profit.
Nominally, this would have to be a very evil exchange, but this kind of thing can happen for example, if the exchange gets hacked.
Why does temporarily halting the network = drive the price down to 0? Once it is halted, people could simply take action and vote out the evil witnesses. While similar to >51% control in PoW the outcome for halting a DPoS network appears much less appealing...