Just read this:
http://www.msnbc.msn.com/id/36832300...in_and_beauty/

Kind of scary that there's no regulation or standards. Also didn't realize that many sunblocks didn't work on UVA, which is what causes wrinkles. I admit I thought that the SPF numbers were exponential and was really surprised to see how small of a difference there was between 30 and 15.