I bought my first online sub with a UPS COD. The guy shipped it to me and after I gave UPS the moniez, they gave me the sub (old school w6 //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif) and he got his cash. Did the same with my Pioneer D series comps too now that I think about it. Seems legit.
1. It costs extra to burden UPS with this extra work.
2. You have to pay out of pocket to ship the item and wait for 10 days in some cases to get your funds. If the buyer actually pays or you are just out shipping costs.
3. It is a huge headache and has it's own set of issues that will arise and it can make getting scammed much easier.