Participating in Datacoin sounds legally dangerous. All a miscreant needs to do is include into its blockchain some files that are illegal to possess, and everyone is potentially in trouble.
Such link could be sent with a bank transfer too - I don't think you could then claim the bank holds and spreads the links to child abuse. Or could you?
That's an interesting scenario, and I don't know how much distinction is made between possession of illegal material and possession of a means of instantly retrieving it.
Datacoin has the storage capacity to include the actual images as part of the blockchain though, not just (probably quite ephemeral) links to such.
It would be like this, but worse: http://www.dailydot.com/business/bitcoin-child-porn-transact...