Plasma did have an issue with 'burn in' on static images. If you did a lot of gaming on them, you could see it. Same with banners on news programming.
If you watch a lot of movies, it isn't an issue. Plus, the TVs came with a 'burn in' reduction program that you could run a couple times a year, but that operated by sweeping an intense white bar across the screen, so you were effectively 'wearing' the pixels down to a similar level to reduce the obvious burn in. If you ran that cycle to often, it would kill the maximum brightness.
If you watch a lot of movies, it isn't an issue. Plus, the TVs came with a 'burn in' reduction program that you could run a couple times a year, but that operated by sweeping an intense white bar across the screen, so you were effectively 'wearing' the pixels down to a similar level to reduce the obvious burn in. If you ran that cycle to often, it would kill the maximum brightness.