Luckily it still costs a lot of money to reproduce things exactly and most fakes will be spotted in hand, which is at least
useful when buying online where you have the refund policy (ebay)
As far as I know this was probably the most accurate replica MOC - http://theswca.com/index.php?action=disp_item&item_id=51431
Even so, there are some tell tale signs that this isn't a real figure- but I must admit it looks pretty good from a simple picture.
Be wary but not afraid is the answer, in hand most of these won't get by anyone with access to other MOC, a forum or google to compare pictures.