I was always told that if a static image is left on your computer monitor screen or TV screen it can burn an irremovable image on the screen, hence screen savers.
How can one then listen to digital radio via the TV, or watch TV programmes that have a contant station identification in the corner of the screen, without causing damage to the screen?
It's not as huge a problem as it used to be but it's still a risk.
As long as the screen isn't used for only the one thing to the exclusion of all else.
I read once of pubs that showed Sky Sports on big plasma tellies complaining to Sky about the ever present Sky logo being burned into the corner of the screen.
It's a problem with any screen that contains phosphors. LCDs don't, so don't suffer from this problem. However, they can suffer similar problems for different reasons, but it's far less likely to happen.