I think even the usually pragmatic Swiss are staring to loose their common sense in this matter:
I fully agree that people should not be taking their whole household on board, particularly not in economy; however, I find airlines should take a pragmatic approach with premium passengers, top tier frequent flyers and special cases (e.g., families with babies, etc.), and this should be possible with check-in staff being granted the discretion to (continue to) use their (common sense) judgment. One of the main ideas behind the restrictions is to make the boarding and deplaning process as quick as possible, so as to make turnarounds more efficient (some of you may know that Swiss has introduced new deplaning procedures to try and shave off a few minutes and turn the aircraft around faster: planes on the ground don't make money...). A few centimeters here or there or a few grams here or there will, in moderation, generally not make much of a difference, but will maintain a lot of customer goodwill. Also, check-in staff should take the load factor (which they can see) of particular flights into account: I can understand them being stricter on full flights; however, on half empty flights it is simply ridiculous.