Dark wallet is a centralized mixing service where you use a browser extension to anonymize transactions. Look at this screenshot:
http://i.imgur.com/FA7TIA6.png . You can see it's routing all of the traffic through gateway.unsystem.net.
So here's our advantages vs dark wallet:
1.) We're decentralized. The clients automatically discover all masternodes and will use those
2.) Everyone will use DarkSend by default. The problem with a product you must setup like this is you'll have far fewer legitimate users to mix with.
3.) Masternodes create a new type of investment opportunity within our ecosystem much like mining. The result? We get a ton of super high quality full nodes, anonymity and happy investors.
4.) If they're accepting inputs and outputs separately they can be shut down simply by a user offering an input, but refusing to send the output. If they're accepting inputs and outputs together, it's not anonymous and it MUST be decentralized to spread the knowledge of who did what to keep anonymity. My guess is they're taking inputs and outputs separately and banning inputs that do this. In that case you could attack it by using another mixing service to get fresh inputs.
