Yes, the modern Plasmas far more susceptible to "burn-in" during the break-in period and one needs to take care. After a while, it won't burn in nearly as easily as the modern plasmas are designed to prevent burn-in from happening so easily. However, just about all the modern plasmas have some feature that runs for some time that will attempt to remove the burnt image. If your plasma does not have such a feature, you could leave the TV on to some sports channel (something that has lots of action and movement to excites or uses all the pixels for a long period (hours, like overnight) or, perhaps better, purchase the Disney WOW Blu-ray calibration disc (at Amazon or brick and mortar Best Buy, for example). The Disney WOW disc has a section that you play on the TV for quite some time (hours, I think) that will attempt to remove (refresh the screen ) any burnt images on screen. It is supposed to be effective in on LCD's, which can also suffer from burn-in, but not nearly as easily as plasma.
Please, best of luck to those with burnt images on the screen.