You could
probably make a coincident-voltage memory from them... but
 they'd be slow I think, but pretty. 
 Not all that slow.  The first plasma
panels -- invented at the
 University of Illinois and used in the PLATO system terminals -- used
 the display pixels as memories. 
 
Yes-- and they were pig-slow.  (I used PLATO in the late '70s, and even
then it felt slow to me.)
/~\ The ASCII                           der Mouse
\ / Ribbon Campaign
 X  Against HTML               mouse at rodents.montreal.qc.ca
/ \ Email!           7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B