I was looking at buying a miner with Btc - but I realized I have no guarantees at all about what I will get.  You know, with Amazon there's that return guarantee and all, but there's nothing with bitcoin.  If you order something, send the Btc, then don't receive the product, you can't ever get the Btc back - how do you know an online sale isn't actually a scam?

Thanks! 
noob