This is one of the stupidest "security measures" I've ever heard of in my life:

Yankee fans are seeing - and turning - red over a ban on sunscreen, which Stadium security guards say was widely expanded in the last few weeks.

Security guards collected garbage bags full of sunblock at the entrances to Yankee Stadium over the sweltering weekend, when temps hit 96 degrees and the UV index reached a skin-scorching 9 out of 10 - a move team officials said was to protect the Stadium from terrorism.
...
The team contends that sunscreen has long been on the list of stadium contraband, but there is no mention of it on the Yankee Web site.

That's right.  They banned sun screen, at an outdoor stadium.  To quote one doctor:

Dermatologists said that, security concerns or not, leaving 56,000 fans unprotected from potential skin cancer is "very dangerous."

"This is especially bad for children, as their younger skin is particularly sensitive," said Dr. Babar Rao, a specialist at the Skin and Cancer Center of New York. "Sunblock needs to be reapplied every two hours, even if you are not swimming in the ocean or pool."

So why on Earth would they do this?  Is this to mimic the airline ban on liquids and gels?  That ban by the way does absolutely nothing to protect our safety as no one has yet to find a credible way to take down a plane with such liquids.  But I digress.  This isn't an airport we're talking about.  So why on Earth would they do this?

The Stadium does sell 1-ounce bottles of Arizona Sun SPF 15 for $5 - a huge markup that makes its beer seem cheap.

Oh.  Well... now it makes sense.  Luckily, after this article came out, the Yankees reversed course.  Via Bruce Schneier.