I dont think changing the age is the right thing to do. I think parents need to help children make that transition of them being responsible to the child being responsible, and it needs to start way before 18. The parents that completely turn over the power on one day, the 18th birthday are asking for trouble.
I also agree with this. I plan to give my children freedoms and responsibilities gradually over the years so that by 18 they are ready to be treated like an adult.