What can be achieved though, is keeping your finances private from your neighbors, friends, relatives, employers, competitors, insurance company, bank, police, local authorities, irs, etc, and to keep your coins actually fungible. This is the flaw of Bitcoin that Darkcoin aims to fix.
I don't believe it can have any confidence of even doing that, because there is a reasonable probability that masternodes will ultimately be owned by corporations in the business of mining data for profit. The whole internet tracking and tracing industry didn't start out that way either, it happened over time because it was profitable. Many early pioneers on the internet were advocates for privacy and individual empowerment, but in reality the internet turned into a massive surveillance machine, not only for the NSA, but for business too. Masternodes are the same.
What you want to achieve can be done trustlessly with cryptography. It can't be done by pretending that nodes operating a for-profit service on the internet are going to remain in the hands of enthusiasts and idealists.