I had the misfortune of purchasing a counterfeit AC adapter from the merchant newmp3technology.com, which also operates under the name newmp3technology. The sample was submitted to HP for authentication and it was confirmed counterfeit. The seller's feedback profile on eBay magically turned to "private". recently. AC adapters and batteries are a special concern as faulty products can cause fire and injuries. Savvy eBay shoppers are becoming aware of existence of counterfeit goods on eBay and many are avoiding fashion brands that are well known to be counterfeited. As far as electronics accessory in general, my practice was to avoid purchasing from newly registered sellers,review their feedback comments and buy from sellers who ship from the U.S. I believe these are intuitions and common sense that develop from experience. I took these measures and I hate to admit that I just got burned. The merchant in question has been a member on eBay for almost 11 years and a "top rated seller" with excellent feedback history. I believe this can be attributed to likelihood that most consumer buyers do not realize what they're getting is counterfeit. The adapter looks adequately authentic at first glance and it is functional. eBay feedback exchange takes place soon after the purchase is complete, therefore it does not reflect subsequent discovery problems, if discovered at all. When you look at this seller's items, you'll see that it uses the claim "Genuine" as a marketing leverage. The counterfeit is not hard to identify, however to prove beyond reasonable doubt is hard and perhaps the only way is to have it analyzed by HP R&D. 1.) I immediately became suspicious, because the cord was only 4 ft and the original cord that came with the computer has a 6 ft cord. The suspected fake comes with a choke(small cylindrical thing around the cord near the laptop plug-in end) 2.) Next is the weighing method which was mentioned on some YouTube videos. I weighed both OEM while holding the cord with my hand with a bit of slack to subtract the weight of cord while minimizing the effect of pulling on the cord on weighing. This had to be done, because 4' cord and 6' cord won't weigh the same. OEM is ~180g. The suspect is ~160g 3.) Grammar and spelling. SA *EE* TY Mark. No, it is not misspelled on the OEM version, however, as you know, spelling errors can happen to textbooks and real stuff too, so even this isn't absolutely positive. 4.) Electrical testing. When loaded with a resistor bank to approximately 60W with resistors, it was found that the OEM drew 70W, the knock off drew 73W. The knock off is labeled "efficiency IV" which indicates >85% efficiency, but remember that my OEM cord is from ~2004-05 when efficiency regulations were slightly less stringent. ^ link to photo for non-members who can't see attachments. Four months later.... label starts blistering. I decided to tear it down. Quality indicates its definitely not OEM. After a few month of use, the label started to blister like crazy. I peeled it off, then put it back on, but it blistered again. Typically a power supply will have an inductor right where the jumpers are to minimize conducted EMF emissions in order to satisfy FCC requirements as well as reduce interference. Does this look like HP OEM product quality soldering job? One of the SMD was actually not seated all the way with way too much solder as well as being crooked. Not what you'd expect from quality automated manufacturing. The artifacts from manual trimming with diagonal cutters are obvious on larger components. This looks like a practice circuit board from an electronics 101 class. Discoloration was obvious along the capacitors on the output stage.