@tinson ... Loco is absolutely right. Most on line stores are considered "distributers" and not retailers so their not factory authorized. If that is the case, make sure that their own warranty is at least as good as the manufactures. Take a look at their home page and see if you find the words "Factory (or manufacturer) Authorized dealer" ... they always have it in bold and obvious print because a lot of people (like me) won't buy it otherwise. Also, look for the gold "BBB" shield also in an obvious place.
Damn, some of their prices are really good. I've been considering the Sharp Aquos(sp?) so I checked them out ... at least the one TV I looked at had the manufacture's warranty though I didn't look closely at the others.