Might present a security risk. Burn-in persistence on CRT screens was a serious concern in olden times. Once they entered a SCIF, monitors were not allowed to leave, at our site. I participated in experiments using flash UV to try to detect latent images; what worked better, though, was manipulating the electron gun from the back of the CRT to produce a flood beam.<p>Williams tube memory (before my time) and Tektronix 4014 terminals worked by similar physics.<p>Time to update the policies &amp; procedures to include LCDs. OLED, when it arrives, will almost certainly exhibit the same effect.