Mis-sold gadgets and tedious setup?
I wonder how many people get home with a cool new MP3 player that won't work because they're still running ME and it's not compatible, or buy a nifty new wireless router only to find their home is made from solid lead so it can only be used line-of-sight?
Granted, products do tend to be labelled better nowadays (I find, at least) but to those not in the know the limitations of some gadgets may not always be apparent.
Then there are the products sold by implication -- like the (not particularly technical) friend of mine who bought an iPod touch, and was mislead by the adverts and such into thinking she could use the internet and email on the move (as it happens, she likes it anyhow). I'd have wound her up about it, but I've heard that kind of thing happen before.