I've bought quite a few knives on there and have had only excellent experiences.
As with any transaction, one should is to look at the information that's available when considering where to take their business . In the case of eBay it's feedback, in the case of other non-eBay sellers the GBU forum here -- to see if there's any history of poor service or questionable business practices. As far as fakes, the main thing there is simply to use common sense: if you see a "Strider SMF", "Emerson Commander", "Darrel Ralph Custom Gunhammer", or some other well-known knife being sold for a tiny fraction of its normal cost, there's a good chance it's a fake. Outside of a handful of iconic knife models, wholesale fakes of extant knife models aren't as common as many people seem to fear. Much more common -- but also, thankfully, much easier to spot -- are cases in which somebody illegally slaps the name or logo of a well-known knife company on some Chinese or Pakistani knives that bear little or no resemblance to any model in that company's actual lineup.
EDIT: Looks like others made many of the same points as I was typing my reply. :thumbup: