As Gijs correctly points out in bug 1421737, adding cookies to the site data manager could cause performance problems on heavily used profiles and/or slower machines. Instead of rendering thousands of DOM nodes into a richlistbox, we should consider rendering this list with a <tree> element instead. Another benefit of this is that we get multi-select and other features that richlistbox currently lacks, the obvious downside is that we lose a little flexibility in presentation.

Assigning a priority to get this off the triage list.

Talking to Mossop we might not want to add another fresh <tree> to our code base... I think we want to look into improving the performance of that richlistbox instead....