As a guy who uses firebug, I'd much rather download a special built executable of firebug for myself, once, than spend a lifetime cleaning up relatives browser bars.

(edited to rephrase, what I'm asking for is a market bifurcation where stereotypical end users can't install toolbars and stuff to get owned, but devs are given the ability to screw their browsers up. Or we simply distribute dev tools separate from end user tools.)