KLM, for one, did allow small dogs in the cabin, subject to a load of conditions. Brokenspectre you raised this point once before I think? It has nothing to do with 'celebs'!!!
If, after having been accepted for travel by the airline, a F/A, (such as dolly737 perhaps?
), then tell me that a pax had complained, allergy etc. because my dog was in the cabin and wanted to offload my dog I would 'go to town'! It used to be one of the conditions of carriage that for a dog to be in the cabin at all there had to be sufficient empty seats etc. to allow for other pax, or the pax with the dog, to be reseated to avoid any problems.
And, quite apart from that, travel on todays modern aircraft, with recirculated cabin air, you are likely to be exposed to all kind of bugs/mites and exacerbate all kinds of existing allergies, so who are you going to sue, more specifically, how are you going to prove it? To blame it on someones pet dog, particularly if you don't happen to like dogs, is quite pathetic.