I bought a Nano from an online auction site that need not be named (rhymes with "e-pay"). Just before my purchase arrived I got an email, saying in part,
In this case, the listing was removed because the copyright or trademark owner of this product reported that the item may be counterfeit.
Oh well, it arrived the next day. I loaded the example Blink and Serial sketches, and it works, so I guess I will keep it (sending it back would be more hassle than the $18 that I spent, even if I eventually got the money + return postage back). I don't know if the alleged "counterfeit" was against the Arduino trademark or the other name on it (Gravitech).
And "e-pay" already has a very similar listing back up, but with a different seller name.