How would the winner be selected? And how would it be a fair and equal opportunity for all to have a chance to win?
This could really only be done in a public draw with a notary and all that, because people
invest spend money for that. If it wouldn't be like that, it would leave "enemies" of MOON with ammo. Or even disappointed people discrediting Mooncoin perhaps, because they didn't win. So I would really not recommend this kind of promotion, unless all necessary precautions are taken, to make it absolutely transparent and being conform with the rules in the country where it takes place.
But we are now as start up ..donation as giveaway (illegal?)., it is not a continuous activity that needs to be regularized...i think (italy)
Even if it is not illegal in certain countries, it would be problematic because of the above mentioned reasons. And since Mooncoin is international, there can be participants who originate from those countries, but possibly don't know about it being illegal in their country. It's the same with online-gambling.
It would be better, if a single sponsor does this alone. Then the participants don't have to invest money - what really makes the difference for being possibly illegal or not in some countries.
Maybe one should consult a lawyer for checking this, before going live.