In previous generations you could use pokecheck to check if the Pokemon were hacked. In X&Y so far we can only hack check the Pokemon with the Kalos pentagon. Hopefully when pokecheck is updated for X&Y we can then use it like we have in previous generations.
Cloning is a problem when related to hacking. You could clone a hack and trade it around which has happened here and it's frustrating hunting them all down. As for cloning itself, there is a drawback because the trade value of Pokemon goes way down when you basically have an unlimited supply of them. But then you have generous people who can clone and they give away everything to others who can't. Cloning is not hacking and so cloning is allowed here.
well yeah. i am sceptical about cloning. but i wouldn't got the event legendaries without knowing someone who can clone though. but for the rest of the pokemon i don't really want clones. besides clones are not that expensive than normal shiny or event pokemon though, i want them to only exist once if possible.