To be very careful who you buy from on the internet.
I don’t want to scare my friends who, despite all of my work here and over dinner, continue to believe that the internet is merely a large scale scam populated only by people who want to rob you and steal your indentity. Some of my friends place bungee jumping and internet buying in the same risk category.
Having said that, one of my long-standing rules is to either buy from a known entity like Amazon, Newegg, etc. (even if the item costs a few more dollars there) or do an extensive Google and Newsgroup search on the seller. In fact, I feel much more comfortable buying something from a high feedback (number and percentage) seller on eBay than from some company I’ve never heard of.