A rather funny, though true - article from SFGate:

On the contrary. People who do things badly, Dunning has found in studies conducted with a graduate student, Justin Kruger, are usually supremely confident of their abilities -- more confident, in fact, than people who do things well.

Read the rest for the details. 

I have a pet theory about this for laughter, by the way, if anyone is interested.

People who let you know that they said something funny - by laughing at their own joke, thus advertising that you are supposed to smile/laugh as well - basically aren't really funny  (this is funny - it's your cue to laugh! hahaha - uh...ha?). 

I'm a little ahead of the curve - at least I know I am only mildy humorous - if that!  T

This pet theory is probably less true for women though.

At any rate, very good evidence for 360 degree assessments.