I've found sales folks at stores don't know what they are talking about a lot of the time, so while I appreciate a knowledgeable guide, I can find that just as easily with an online review from a trusted source. I'll admit I like shopping at stores for other human interaction, like chicks.
I wouldn't buy a big screen TV online, but I have purchased monitors and they arrived in perfect condition. But the hassle of returning a damaged big screen wouldn't be worth it to me.