A:
Burn in/image retention is something that is often talked about and scares a lot of people away from plasma. While this may have been an issue on earlier generation plasmas, by this point they have minimized this to a great extent.
Even if you do have a static image on the screen for a longer period of time, if you have the brightness turned down off the "torch mode" that is enabled for display in store, most image retention is only temporary and goes away after you watch a full screen TV show where the pixels get exercised. It is VERY RARE to get permanent "burn in" where the image is actually burned into the screen permanently. From my experience you'd have to intentionally try to get permanent "burn in", while you may notice temporary "image retention" that goes away after a few minutes and isn't a big deal.
TV, Blu Ray and other device manufacturers have done a very good job of creating features like pixel shift and others to minimize this so it is pretty much non-existent, and if you do notice anything it is temporary rather than permanent.
I noticed temporary image retention once on my 8 year old Panasonic Plasma, however it was very temporary and went away after a few minutes. I haven't noticed any on my new F8500 plasma, and the fact it's 8 years newer there have been a lot of technological advancements over that time to address this.