execCommand("paste") should log an error when disallowed
Right now we just silently fail. Which makes web author's lives harder than necessary.
I've related bug 11335.
The current spec requires either throwing SECURITY_ERR, or treating it as unsupported (which if you look at the execCommand() definition means throwing NOT_SUPPORTED_ERR):
Firefox 7.0a2 throws NS_ERROR_DOM_XPCONNECT_ACCESS_DENIED. If you think logging an error is a better idea than throwing, please explain why and I'll consider changing the spec.