I've noticed many differences in spotting a fake Prada on ebay.  The first thing you need to look at is the inner lining.  Most authentic Prada's have a thick, or how I call it crunchy like, inner lining.   It should say PRADA all across with squiggly like decals inbetween each Prada print.  It also will be printed upside down on some lines.  Most fakes have thin lining with no print.  The next big thing is the metal logo, buckles.  The paint/ink on the buckles should be nice, even and smooth.  Look at it too.  If the paint/ink looks like a blob it is a fake.  What I mean is that if you rub your finger over this metal logo and you feel the Prada name raised up a bit it is a fake.  Prada makes these buckles perfectly smooth and securely attached to items.  Sometimes fake logos are so loose that with a nice tug you can pull it off.  Look at stichting of the purse.  Prada uses thick like stiching and pretty much looks perfect all across.  Fakes have poor stitiching and threads usually stick out from them. Look at where the material is cut and check if it is properly tucked.  Look for glue sticking out from corners or edges.  Real Prada's never leave any glue residue for viewing.  Most of hardware will have Prada engraved on it.  Again on fakes look at each letter and make sure it is aligned.  Fakes usually are sloppy when it comes to details.  Look for small cut samples of leather material attached with the price tags.  Prada DOES NOT EVER add samples of leather to their purses.  Hope this helps!