The Ham Shanks wear their medals and every badge they own on their blues and I think it looks a bit silly (though one can apparently tell a guy's service history from them - perhaps quite useful to shut gobby ex-UAS peeps up).
I do, however, sign up to the metal badges on blues idea, for aircrew (not FCs though, I said AIRCREW
), and those blunt (with respect) trades and branches that already have a badge or flash issued. Also agree with sittingstress (please don't tell my friends I agreed woth a Rockape).