Yes, it will be some kind of blockchain spamming. but who cares? The file to be uploaded will be some bytes, not even a kilobyte. But it would demonstarate the functions of datacoin to the world. With krypte.net its pretty easy...
I think the problem of paying the reward in datacoin is, that a user who doesnt know about datacoin, will not do much to get some datacoins. Bitcoins on the otherhand are well known, and users know their value.