TorBrowser_en-US.app V.1 on Snow Leopard saves some bookmarks unasked
I noticed that this command
for x in find . -type f
; do grep -l '.onion' $x ; done
run from
/Applications/TorBrowser_en-US.app/Library/Application Support/Firefox/Profiles/profile
indicates that the urls of several sites I had visited had been saved in places.sqlite and in several bookmark backup files. Deleting places* didn't remove them, only that plus deleting all bookmark backups did the trick.