I've seen lots of people use caps for more than half their sentences so that sometimes less than half the words in the post are lowercase and the balance is capitalized. People do it to emphasize what they are saying or sound excited, but the post comes off looking like they are yelling and is difficult to read.
An example:
I BOUGHT this BAG!! Isn't it WONDERFUL!! I LOVE this bag SO MUCH!!! I'm going over to the STORE and GETTING one EXACTLY like this RIGHT NOW !! I am SO EXCITED!!! : ) This BAG is SO GREAT.!! OMG WHAT HAVE I DONE??!!!??
The reply toolbar contains other options like Bold, Italic and Underline. Maybe they should learn to use those features more....