This is a good thread. I've bought auto and bike parts on eBay and Amazon without trouble, but there are YouTube videos of people unboxing obvious fakes. There are a lot of counterfeit high-end spark plugs on Amazon ... selling super super cheap. I agree with the people who emphasized how important it is to look into who you are buying from. If it is shipped by Amazon, it should be fine. And there are a lot of LBSs who have turned to eBay and Amazon to help keep their business afloat. My wife and I sell jewelry on eBay and etsy, and we are able to make a great income, and put our kids through college. Best bet is to read the feedback carefully.