How do you avoid sites selling counterfeit crap? It's easy, I only shop with reputable companies like all the ones listed on our commissioned buying links list (here). Problem solved. 
A study by brand-protection company MarkMonitor estimates that businesses will lose $135 billion in 2011 due to fake merchandise sold online, as Katie Deatsch reported last January on the Internet Retailer site. I was unable to find the original report quoting that figure on the MarkMonitor site.