I talk like a truck driver with my friends. But generally I keep my profanities to a minimum as much as possible in the workplace or in a public place. However, I use profanities for either when Im upset about something or for an exaggerated comical effect.
Such as:
Shel90's "Lucky bitch!"
or
Friend: "Oh hey, I forgot to bring the toothpicks."
Me: "Omg WTF noob?!"
Although, Jillio is right about someone over using profanities being socially awkward. This guy I know used the f word an excessive amount, in NORMAL conversation. "I was watching the f tv last night, and ya know the f'in show Lost? Yea f man, its a f'in good show." It just comes out strange rather than evidence of low intelligence.