I would have rated this MUCH higher, but there's one security flaw that I'm not thrilled with.
When your extension is running it is showing the referer header being observed in the GET requests, and I currently have those blocked with RefControl, but your extension ignores any other extension out there that blocks the referer header.
As far as Ricky28269's review about it locking up flash, that's actually a flash issue, and not related to your extension. If Linux users update to the latest flash player, it should resolve most of the freezing issues.
I'm not familiar with that extension, but either, TamperData is called before the other extension, meaning the headers haven't been removed yet, or the other extension doesn't really do what you expect. TamperData reports the data it gets from Firefox, it has no direct interaction with other extensions because in general, extensions don't work that way.
Categorizing this as a security flaw is misleading, and inaccurate.