I bought my Samsung 191T from Best Buy, and was going to buy the service plan until I found out it covers exactly what the manufacturers warranty does. I was told they go by manufacturers guidelines for bad pixels. If they are telling you 10%, then they don't know what they are talking about. How would they even know if 10% are dead, and not 9%, are they going to count them? Both my roommates work at Best Buy, I used to work at Best BUy, and I also know a ton of people who have or still do work there. They honestly don't know a lot of stuff, because Best Buy has a bad habit of firing management, and changing policies.
You should also read the service plan brochure and see what it says. I know there is nothign in there about 10% failure. The good thing is they will definitely give you a new LCD if something happens, and they will replace it on the spot. I decided taht for $100 I might as well just send my LCD to Samsung, and then buy a temp crt monitor.