So far, fakes can easily being detected base on its built quality, colours, material, engraving on the backcase, shape of the screws..etc. Basically I won't be worrying when buying from a Live G-Shocks seller which have hundreds or thousands of viewer, they won't sell fakes to destroy their business reputation.

If you're dealing with COD, of course you can actually check all these before paying but if you're buying online with strangers then you have to cross your fingers then.