Why is there a tabbrowser component in core? If it's the sm tabbrowser, it should be under the sm product; otherwise, it should be under toolkit. BTW, what's with https://bugzilla.mozilla.org/show_bug.cgi?id=282178 tabbrowser synch bug, which has a 'XP Toolkit/Widges' component in the core product? That's not right...
The Core:Tabbed Browser component is about bugs in the Suite/Seamonkey UI, so it should move to that product. Firefox bugs live in Firefox:Tabbed Browser.
there's a bug about moving ff's tabbrowser component to toolkit, at which point the xpfe widgets bug could move to that component. (and then when seamonkey switches to using it, the seamonkey component could die.) the reason this component is in core is because it didn't get moved during the great reorg.
Except that I expect to move tabbrowser out of toolkit at some point, so that bug should be wontfix.
This has been fixed as part of the BMO reorg in July 2008: http://www.gerv.net/temp/bmo-reorg.html