I am an avid buyer of sneakers on eBay, especially the rare ones that are out of season and therefore unavailable elsewhere (ie. retail outlets).
This is both eBay's forte and folly - sellers flock to this online auction site to peddle their wares, but with the honest come the greedy... From my own experience, I have learned that 100% authentic still does not always mean 100% authentic in the way it is generally understood in the 'real' world. There are simple rules to follow to avoid the factory second and downright fake items.
1) Feedback, feedback, feedback - I guess this goes without saying. But, other than the 90+ percent feedback rating, look for other things like: does the feedback come from just one country? Are the items all low-level or cheaper items whilst the buyer is trying to sell you a $300 plus item? It's always good to look into the details of a seller feedback, what items they've sold before. If they're a private feedback seller, i'd be very wary and generally avoid them. Also, the seller having 95%+ positive feedback and 50+ entitles you to free PayPal buyer protection which means you can claim directly from the PayPal service if something genuinely goes wrong.
2) Do they say the item is authentic? - What kind of words do they use? 100% Authentic or just 'original'? Does it come in the packaging, with tags? Many sellers acquire factory second items meaning they are produced at the same (mostly) third-world labour factories by the same machines, without the blessing of the brand's owner and with consistently poorer quality materials. If there is no mention of any topic relating to the authenticity of the item in the description, it is doubtful the item is authentic. I've purchased factory second shoes that the seller claimed to be 100% Authentic, and from the photographs they might as well have been. Upon receiving them, I discovered the poor workmanship.
3) Photographs - Always ask for detailed photographs if possible. This demonstrates two things: the seller has no hesitations about scrutinizing his item and you can see for yourself if the item is authentic. Select items that are hard to fake or a general indication of the authenticity (eg. Symbols, serial numbers, production codes, 'swoosh' =)
Here's some other things you can considers but are not always a true indicator.
- The items's country of origin - there are SOME countries (for the purposes of political correctness, they will remain unnamed) that consistently have fake products ready to ship. Avoid.
- The starting price - There's a ton of particular designer jackets selling on eBay for $100-200, all claiming to be 100% authentic. Retail prices START from $800+. My friends each bought one in full knowledge that they would most likely be fake. They were. Lesson? Some things are just too good to be true. If something's selling for way below the cost price, and it's still quite a popular item, then the seller's either on eBay looking to lose money or selling fakes.
Thanks for taking the item to read this quick guide. Sorry if i've rambled on a bit in some places and have been to brief in others, I'm writing things as they come to mind. Hopefuly I've enlightened you in some way - the main thing is to use your head. Good luck, hope you find what you're looking for.