I think most people who use all caps are fairly new to message boards and chat rooms. Of course I suppose there are a few who just like to be annoying, but normally if you tell someone that their caps are not being well received they'll switch.
Now when I want to be annoying I play with text decorations. If you jumble them up and [li]use a lot of them[/li] you can really give people [ol]headaches.[/ol] I guess the worst would be to [ul] [ol] [li]use as many of them as possible at the same time. [/ul] [/ol] [/li]
Sorry....just messing around because I am bored today. I really do agree with you Cheryl, reading all caps is hard on the eyes and can make you not want to bother.