I'm really dumbstruck by this one. I see it everywhere now, though. The last time I bought a monitor, a Samsung 1941BW, it was just 19-inches widescreen. Before that, LCD's, TV's, and CRT's where advertising "viewable" or "diagonal" area, and would often come with a sticker or logo which described the diagonal line, and where I should measure if I wanted to check for myself.
But, how the heck do I know what a 22-inch class monitor is? I just bought a TV which is 19-inch "class". What is this? It's even on laptop ads now.