I've made the "#SharedObjects" directory read-only.

Since then I've been using flash without any problems - the only noticeable effect is that I have to reset the volume on youtube videos each time I play a video.

I bet future versions of browsers would clear such cookies as well. Flash is almost a standard feature of every browser now.

Including the Chrome 'Incognito' mode?

Not an expert, but I'd imagine so. Unless they do some wicked hackery, Chrome can't restrict what a Flash plugin executable does with an SWF file.

you are correct. chrome does store flash cookies even when in incognito mode. i logged out of pandora in chrome, started up IE, noticed that i was logged out of pandora, then started up chrome in incognito mode, logged into panodra, then started up IE and noticed that i was now logged in to pandora.

Is there an easy way to test this?

Play this (addicting) game in Firefox - http://www.ferryhalim.com/orisinal/g3/bells.htm. It will record your high score. Open Chrome in incognito mode, die quickly, and see that it has kept your high score from Firefox.

CCleaner works well at deleting all those cookies that sneak by private browsing.

Not flash visited sites. It may have deleted Flash cookies but the flash check cookies link listed here still shows sites after a CCleaner run.

See http://forum.piriform.com/index.php?showtopic=22980.

Ok I'm back, after 'experimenting' with that flash game for the last 19 hours I can report that the music does get a bit annoying after hour 13 or so. Also Incognito mode doesn't stop the flash bugs.