Mr. Wizard, I've been singing that song for several years.. And the evidence is that if Human activity has caused any change in speed.. It is very very minior (I could not see any discontinuity in the graphs I viewed.
On the issue of light bulbs.. The thing.. This applies to 120 volt lamps in teh 20-100 watt range (Might be 15-100 watt range) I have a grand total of ZERO of those in this motor home.. All my 120 volt lamps are:
Florcesent (And under 15 watts) or
9Watt 7.5 watt or 4 watt Christmas tree lamps (or smaller) OR LED (Tree lights) or 150 watt (Flood lamp) Not one lamp is bothered at all by this rule.