I think using exclamation points in writing is often the equivalent to jabbing someone in the ribs and saying "You're supposed to laugh here," or "You're supposed to be shocked here." It's a crutch for people who know they haven't evoked those emotions with the actual prose, or at least feel insecure about their ability to do so.
Exclamation points are great; don't get me wrong. If I write to friends on Facebook chat or MSN messenger and they respond with "Hey!" it puts my mind at ease that they actually want to talk to me. Plain ol' "Hey" is just polite. Laid back polite. "Hi" reads curt. Almost angry. But, "Hi!"? It reads much more friendly, but also kind of sarcastic for some reason. "Hello" is also a bit cold, but it shows more effort in typing because there are more letters in the word. You wouldn't put that effort in if you didn't want to talk to someone would you?
If you write my name after "Hi," or "Hey," I'll know you care. Plus, it will also show that you remember my name -- or at least remember how to spell it. My name is Ashley Ashbee and people tend to confuse the second syllables: "Ashlee" for my first name or, less commonly, "Ashbey" for my last name.
I'm actually not neurotic, though.