Even if it were to be documented, I imagine it would read something like:
"This API works exactly like this. Except when the user disables local storage. Oh wait, also not when the Flash version is 11.0.635.24.b. Well, also it's different if you don't have a security-inst-config.xml installed in the home directory of the user under the path .adobe/flash/securityPolicy. OH! Also it works completely differently if you're using HTTPS. And it won't work at all if you're trying to access any server without a security policy defined on the DNS TXT record third from the top. Also there are some slight issues between 3 and 5 PM GMT on Tuesdays, but a workaround can be found on the Macromedia support forums."
"This API works exactly like this. Except when the user disables local storage. Oh wait, also not when the Flash version is 11.0.635.24.b. Well, also it's different if you don't have a security-inst-config.xml installed in the home directory of the user under the path .adobe/flash/securityPolicy. OH! Also it works completely differently if you're using HTTPS. And it won't work at all if you're trying to access any server without a security policy defined on the DNS TXT record third from the top. Also there are some slight issues between 3 and 5 PM GMT on Tuesdays, but a workaround can be found on the Macromedia support forums."