I have fallen into the lazy Mac user's habit of never turning off my computer. If you're a Windows user, this may strike you as bizarre. After all, Windows performance degrades the longer you go without a reboot, and every minor hiccup in a program seems to require a system restart. But not so much with Macs.
I had turned off my screensaver, I can't remember why, I think it was interfering with some mega-giga file transfer. Then I left a text document open overnight. When I went back to editing photos the next day, I saw all these faint horizontal black bands in my skies. My LCD had burned in the pattern of the text.
Paul Butzi pointed out this phenomenon of LCD image persistence last year in his blog, and aimed me toward the solution: a screensaver that “exercises” all the transistors and pixels, and erases any image persistence issues. It's called LCD Scrub, and it works. Today my screen is squeaky clean, at least electronically. Now if someone could point me to a solution for maintaining a streak-free exterior.