Good Riddles

Question: In Michigan you cannot take a picture of a man in a green hat.

Why?

Question: What goes up but never comes down?

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: What do these things all have in common: Laughter, living well, and a good offense?

Question: 4 people fall out of a boat and only 3 get their hair wet.