Not required in Florida. I make my decison to wear on many factors...weather for one (rain and or cold is a yes). Long journey, yes. I have a couple bikes and when on my crotch rocket, it is a definte yes. Local rides on the Harley (which is 95% of my riding) I do not, even on some longer rides. I like to have the choice but would not raise a huge protest if it were required. It was for a while and it didn't bother me (only when sitting in traffic in Daytona during a bike event when its 90 plus degrees, it does get kinda hot)
On a note about injuries, I suffered a very serious head injury in 1996, not on a motorcycle, so I know all to well what it is like and what the costs and reprocusions can be, having gone through that I still think it should be up to the rider.
On another note (you would think that this would really convince me) let me tell you about how a helmet law indirectly saved my life. I was going to Atlanta for the Harley 100th kick off party. I had been riding with the flow of traffic up I-75 for a quite a while, even had a few thumbs up from some people in cars I had been cruising with for many miles. The guy who I was riding with realized and notified me about 10 miles into Georgia that they have a helmet law. We quickly pulled over to the birm and put on our helmets, back riding immediately. About 10 miles later up ahead of us we see a huge fireball rise into the air. It was a very horrible accident involving 2 semi trucks, 4 cars and a church van. Several people were killed, most of them were burnt. It was the same group of cars that we were riding with earlier. Had we not stopped to put on our helmets, I am convinced we would have been right there in that tragedy as well. I personally will never forget what I saw there the rest of my life. Hopefully none of you will ever have to witness that.