Duplicate Tab 1.0.2c no longer works now that Firefox has reached Version 10.0.1 . Duplicate Tab Version 99.0 still works but its distribtuition vehicle, megaupload.com, has been shut down by the FBI, apparently for violations of law. I have a copy of "Duplicate Tab Max Version 99.0.xpi". As Duplicate Tab is being kept alive by its users and no one is losing money thereby nor, as I understand it, is it copyrighted, if someone will post it on the web for us and put the link here, I will be glad to send it to them for that purpose.
This Extension should definately be a part of Firefox as it is integral to Firefox's use.