God, to think a "mundane" topic like this could generate so much interest and confusion! Cabin lights are dimmed, so that in case of an emergency evacuation after a crash landing passengers and crew can see better as they are already used to the darkness. I would assume cabin lights are also dimmed (to answer the question regarding day flights) is that it eliminates as many potential ignition sources should a forced landing be carried out. I do know that it is NOT done so people can have a good view!! Re. individual reading lights-I have no idea. It could be that the airlines don't whant to come accrosss as completely paranoid, or when some old lady asks a F/A "where is the reading light, dear," that the reply does not put the poor thing into cardiac arrest. Passengers don't care to hear about possible crash landings-it's bad PR!!!