Ways to recover video memory from a shutdown system may exist.
Hence, Tails should erase that memory on shutdown.
Talking with a friend of mine who used to work on video card drivers for X.org (slightly paraphrased, didn't need to take you through the entire conversation):
> < brutal_chaos> MostAwesomeDude: is it possible to erase video ram for all types of video cards during shutdown?
> < MostAwesomeDude> You can't clear the VRAM until the computer's off, because the BIOS will keep writing to it up until the last second.
> < brutal_chaos> Is there a way to flush the vram then?
> < MostAwesomeDude> Basically, become root, find the PCI BAR where VRAM's mapped, and walk over it. There's a couple things called mmapw and mmapr that can help you; Google for them.
