Thrillnetwork.com reports on a disatrous attempt at a Six Flags "free day". The Atlanta Journal Constitution originally reported on the event.
Any economist worth his salt could have predicted many of the problems the Georgia park experienced. When you don't have prices that reflect consumer demands you get chaos, and most consumers get nothing.
Contrary to popular mantra, prices exist for a reason and they can't just be artificially lowered without consequences. That goes for caps on gas prices too. Just ask Jimmy Carter how his gas price caps worked out. (I'll give you a hint...it didn't)
Here's a slide show of the problems caused by free admission.