First of all please set aside the obvious action-happy engines based around conspirator and scrying pool and even minion.
Such obvious cases aside, what are some good examples of decks, kingdoms, and/or game stages in which buying silver -- or even accepting a "free" silver will actually worsen your deck?
We all know Colony games make massing silver less interesting, but can we quantify this more or give good examples of when to "avoid" silver?
For example if you have more Platinums than coppers, silver starts looking pretty meh.