Fine.
Let it run its course because whether it's a fad or not, there are one hell of a lot of people out there who simply are not going to take to a public domain blockchain.
It can go to half this price if it likes, as long as it's not zero because whoever is left standing at the end of the rout is going to pick up one hell of a prize.
You made a relevant point regarding regulators "banning" certain currencies from being used by retailers due to having opaque blockchains which I'd like to answer. That is indeed something that could happen but it's purely hypothetical because the reality is that regulators are not going to let ANY cryptocurrency gain the slightest hold on the real economy if they can help it.
If you think they're going to even bat an eyelid over whether a particular blockchain is opaque or transparent then I don't think you've a very good appreciation of what a cryptocurrency is in economics terms. Bottom line is that there is far too much leverage in the fiat financial system for them to let people get anywhere near any of them, so the whole debate's hypothetical.
All crypto's are for users, not regulators, and it's in that context that Darkcoin has a huge potential market.