Common sense is a subjective problem. It describes your own take on things in a way that makes it appear better than others.

Methinks most people are talking efficient sense rather than common sense, which is as Good Soldier Schweik points out, never common. It can't be because it describes your own view.

Seeing less common sense applied around you is no more than accepting you are getting old. Buying an iPad made common sense to me whilst my father in law saves his money by heating a spare bedroom and having a desk with an old PC firing up slowly and him spending a couple of hours just to do his emails. That's common sense to him, same as having a car that is small to save money whilst questioning my big car on cost grounds. Mine doing 55mpg, his doing 30mpg, mine having lower car tax and insurance, but because his is small, it is common sense and saves him money whilst I must be throwing money away eh?

Common sense is about the most subjective phrase I can think of.

(Mind you, that's the car I collect next week. The 4x4 I have right now is a thirsty bugger....)