Did you read about the woman who was fired for sending all caps emails?
If you've been sending emails since the dawn of time, you know that's a big "no no." However, as irritating as it is, I don't think it should be grounds for firing an employee. Shouldn't she first have been taken aside and told that's "just not nice" to format emails in that manner?
I don't know the details, but I do know that she who laughs last is the one who filed a lawsuit for unjust termination and collects a few grand. Yep, the court found in her favor.
I've found that most people who use all caps in emails are one of these:
(a) too lazy to use the shift key; the flip side of this are the people who use all lower case. That irritates me just as much; e e cummings may have gotten away with it, but that doesn't mean you can.
(b) not proficient at keyboarding
(c) senior citizens who have come to email late in life and don't know the "rules."
Be nice to people who don't follow established protocols. Either guide them gently or ignore the issue.