this would allow specific subsets of bookmarks to be excluded from the location bar.

As with bug 450314, this overly narrow, and doesn't address almost any of the use-cases sufficiently. After talking w/ UX about this, marking WONTFIX. If you'd like this feature, please add use-cases here and we can take a look again for 3.2.

Bug 451915 - move Firefox/Places bugs to Firefox/Bookmarks and History. Remove all bugspam from this move by filtering for the string "places-to-b-and-h". In Thunderbird 3.0b, you do that as follows: Tools | Message Filters Make sure the correct account is selected. Click "New" Conditions: Body contains places-to-b-and-h Change the action to "Delete Message". Select "Manually Run" from the dropdown at the top. Click OK. Select the filter in the list, make sure "Inbox" is selected at the bottom, and click "Run Now". This should delete all the bugspam. You can then delete the filter. Gerv

Sid's "Not Awesome" add-on allows you exclude individual bookmarks from the Awesome Bar: https://addons.mozilla.org/en-US/firefox/addon/14031