Isn't this NP-complete?
Probably.
Poor impotent script kiddies! 
How much would it cost to give each MPEx user their own unique/secret IP address and VPS proxy?
How much would it cost to give each MPEx user their own unique/secret IP address and VPS proxy?
The cost would be more on helping them deal with it. Even with the entry barrier many people trading on MPEx don't actually have a full IT house at their disposal like IRL investment banks do.