The condition of over using the emoticons =P, :P, ;p, and variations thereof to express the fact that you are silly. This is usually done over IRC but it also happens in other mediums. Typically, a standard case of =P addiction has the person using =P on every line, even in greetings, like so:

hey =p

whats up? =p

Personally i'm doing fine. ;p

But at least i'm not serious =p

And on, and on, and on. Most =P addiction works itself out after a few months or years, luckily. But the cause is usually finding someone else addicted and trying to fit in with them. It is incurable except fighting it off of the addicted persons own accord.