My Firefox profile being corrupted, I had to dive a little bit into its salted directory. What I found there is just scary... Here are the contents of that profile:

GoogleToolbarData			extensions				places.sqlite
User_Gear.owg				extensions.ini				pluginreg.dat
adblockplus				extensions.log				prefs.bak
addons.sqlite				extensions.rdf				prefs.js
antbar					extensions.sqlite			rainbow-easel
blocklist.xml				fireFTPprograms.dat			scribefire.sqlite
bookmarkbackups				fireFTPsites.dat			search.json
bookmarks.bak				firebug					search.rdf
bookmarks.html				foo.dat					search.sqlite
bookmarks.html.sbsd.bak			formhistory.sqlite			searchplugins
bookmarks.postplaces.html		foxyproxy.xml				secmod.db
bookmarks.preplaces.html		freerecord.sqlite			sessionstore.bak
bookmarks.xml				gm_scripts				sessionstore.js
bookmarks_history.sqlite		gtb-metrics.xml				signons.sqlite
cert8.db				hostperm.1				signons.txt
cert_override.txt			imagescatch_autosave.owm		signons2.txt
chatzilla				jetpack					signons3.txt
chrome					jetpack-editor-code.txt			tidy_base.html
chromeappsstore.sqlite			jetpack-example-code.txt		tidy_cleanup.html
compatibility.ini			jetpack_ann.sqlite			tplbug.sqlite
compreg.dat				key3.db					twitfactory.sqlite
content-prefs.sqlite			kf.txt					twitterfox_1.9.sqlite
cookies.sqlite				kosa					ubiquity_suggestion_memory.sqlite
cookies.sqlite.bak			lightweighttheme-footer			urlclassifier.sqlite
cookies.txt				lightweighttheme-header			urlclassifier2.sqlite
cookperm.txt				localstore-safe.rdf			urlclassifierkey3.txt
defaults.ini				localstore.bak				useragentswitcher
despin-scratchpad			localstore.rdf				venkman-settings.js
dh-conv-rules.rdf			localstore.rdf~				weave
dh-media-lists.rdf			messages.sqlite				webappsstore.sqlite
dh-smart-names.rdf			mimeTypes.rdf				webchunks2.sqlite
downloads.sqlite			minidumps				xpti.dat
dta_history.xml				permissions.sqlite
dustmeselectors-data			persdict.dat

Hum, to say the least... Ok, some files there (*~ and *,bak) are mine, edited using emacs or another editor because I needed it. But I think user profiles should contain a addon-data/ folder with a subfolder per add-on, its name being the add-on ID of the add-on and that AMO editorial rules should force add-on authors to store *ALL* data there. It would then be easier to migrate, backup, delete, cleanup. Thoughts ? In particular is it ok to put sqlite databases in such a deeper folder for sqlite-based templates (I haven't checked yet)?