I don't recall a post where an LCD owner has complained about their LCD panel being significantly burned in - at least here on C|Net.
That said, it is possible with static images, bright-against-dark gameplay, and other applications if used contrary to the manual. But it is not warrantied if it develops. If you have further questions on the warranty policy, call 800-SAMSUNG and speak to one of the customer service agents.
That said, I invite other LCD owners to submit their experiences, and check your local retailer to see what salespeople have to say. You can also check out their displays, where many retailers play looped demo images to see what repeated images might have done over the last year. Stores generally use the Dynamic (Store Demo) mode, which amps many of the contrast and brightness settings (what we commonly refer to as "torch mode"), so those would likely experience more aging of the panel than the typical home-used television set. I don't think you'll see any image retention on those sets, but I invite you to see for yourself.