Deleting flash cookies (aka, Local Shared Objects or LSO) has always been a twisted and onerous task. I wrote about flash cookies a few years back.
Now comes the welcome news that Adobe has decided to integrate the task of deleting the LSO's with the browsers' delete cookie feature. In other words when you delete your browser cookies using the menu option or ctrl-shift-del, flash cookies will also be deleted along with the standard web cookies and localStorage objects.
It isn't quite finalized yet, but it's in the flash player's latest release candidate, so it should hit our browsers sometime soon.