I would recommend getting it. Eventhough LG comes with a 2 year warranty.
But, ask some questions first.
Is this a performance garuntee (sp? I'm tired) or does the extended warranty just cover parts and labor?
Does it cover things such as power surge?
Does it cover dead pixels?
Does it cover the backlight bulbs?
If the answer is yes, then I would definitely get it.
The average cost of repair for a flat panel is twice, sometimes three times that. So the cost of keeping it in working order for $500 is worth it IMO.
From my experience in purchasing from Circuit City, they do cover these things. I'm not sure on BB extended warranty. (Which they do not get commission anymore BTW)