Just a thought on improving YADB. I'm thinking there may well be many entries in my ML that YADB doesn't have but there's no way for me to find out without manually submitting everything. I'm not sure what submitting 100,000+ tracks would do to my CPU, your db, or the pipes in between.
I'm thinking it might be nice to have a plugin working in the background, on a low priority basis, trying to find matches between a user's db and YADB. Not to change the user's tags but to ask, if no matching entries were found in YADB, if the user would like to submit the info to YADB. Cover art lookups could also be done.
Perhaps the plugin could create a playlist with these entries that you could go over and submit at your leisure. Or it could work while importing files or tagging and prompt you to send in the stuff YADB doesn't have.
I can also see a reminder of sorts built in. You look up art or tag info from YADB and don't find anything. You fill in the missing info and the plugin then asks you be nice and share that info with others.