It's funny...everybody was running scared about park flyers a few years ago, but it SEEMS to me(I don't have any hard data) that they are not the threat they could have been.
Most of the really ready to fly ones are on 27mhz...those with the radio already installed, etc. It does not seem that kids really go for them. Nintendo seems to be just a bit more popular!
I have never heard of an incident where a park flyer at a local schoolyard has shot down a "real" RC plane flying at an AMA field. I'm sure it has happened at least ONCE, but the spate of horrible accidents where turbines are sent spinning out of control into schoolbuses full of nuns because of some kid with an "unregistered" park flyer on 72mhz just did not seem to pan out...