Coins do not need the government or its approval to succeed.
If there's a demand for Zerocoin, it will succeed.
Except if a particular coin is ruled illegal because it is a security risk...it will NEVER be accepted by your neighborhood coffee shop...Overstock...or ultimately some place like Amazon.
So its "success" will be limited to the world of a "Silk Road 3".
Black market was very early adopter of Bitcoin, right? Being adopted by black market will be huge success for Zerocoin, it prove that the coin have real benefit of usage and real potential. Majority of altcoins will be dead because they have no users, no merchants and no customers, they have only investors and miners. They talk something fancy about ASIC resistant and 'cooler temperature' to trick more GPU miners come with them.
Except as I added in my edit above...I wonder what the legal boys and girls think about that at Johns Hopkins. Matt Green was and I believe still is a faculty member at Johns Hopkins...and the others involved in the project were students of his?
Seems to me their may be some concerns about the name of Johns Hopkins popping up in the almost certain articles about the use of Zerocoin for trade of drugs, guns, etc. on the black market?