In France they're illegal around (and visible from) express roads (roads with central separators and at least 2 lanes each ways, generally limited to 110km/h) and highways (same but with more stringent sizing specs, extensive shoulders and usually speed-limited to 130km/h), within 40 meters in cities and 200 meters outside.
I think so, yes, but I feel this way primarily for aesthetic reasons.
I actually find those permanent-installation LED government road signs warning of lane closures and advising of average travel times to be worse because the angle at which they're viewable tends to be terrible and require you to pay more attention to read them than they should.
They are also banned out of urban zones in Spain. There is a survivor sign that was allowed to stay, "El Toro de Osborne". That's how we do it...
http://en.wikipedia.org/wiki/Osborne_bull
So advertisements beside roads should be banned?