Zerocoin would give you this incredible privacy guarantee, then we could add on some features which let the police, for instance, to be able to track money laundering. A back door.
Hilarious.
But, without the back door, it's an interesting idea.
Okay, a little bit of conspiracy is in order here:
- 1st scenario: The guy is incredibly stupid. Only mentioning the possibility of a backdoor in a non open source project, will make most of your possible users run away, we're talking about a crypto-currency after all.
- 2nd scenario: The question was so stupid that he wanted to give back an equally stupid answer.
Either way, I'm never going to use (especially if I can't have a clear look at the source code). However it's a fine proof of concept for similar to follow.