Have you ever written a pithy sentence and got to the end and thought "I want to leave it with a full stop, but I am not brave enough, I may piss people off, I'll end it with an exclamation mark, that way they will see the smile on my face?"!
Listen, if you want to get ahead in life and make as many friends as possible then the exclamation mark is your best friend - every time you make an inane announcement on facebook or twitter then you need to add at least five of those stiff little fucks to the end of it!!!!!
But it's the cowards way out. Do you think Tom Selleck, as Magnum P.I. would ever think of using a fucking exclamation mark? Which of these do you think Dirty Harry, if he were writing his autobiography, would write?
"Blew that dirty fuck's face off."
"Blew that dirty fuck's face off!!! LOL!"
If you write what's on your mind leave it as intended, with a fucking full stop at the end of it.