I sold off any Darkcoin I had last week. Not sure why it's taking off now. Anyway I sold it because the darksend technology is cool and all, but I can't really see the benefit. For anonymous payments you can't really beat cash, and for businesses, saying you now take Darkcoin is another way of saying "If you're ashamed to buy our stuff, here is a solution!" Err, right
It's harder to transmit cash over the internet. Can't send cash in envelopes and money orders aren't normally accepted because of fraud.
I hadn't even considered the issue about people sending cash in the mail.