1. If it was part of trunk, you'd have to wait longer for new updates. As it is, Firebug can push updates without waiting on Firefox updates. 2. The Firebug dev

1. If it was part of trunk, you'd have to wait longer for new updates. As it is, Firebug can push updates without waiting on Firefox updates. 2. The Firebug developers and core mozilla developers overlap a lot. There is work done in trunk that complements Firebug. So it's has plenty of official blessing. 3. There isn't any performance advantage to putting it in trunk. Extensions in mozilla are first class citizens. 4. It would probably confuse ordinary users.