Well, one obvious effect of cats acquiring flight ability would be that they would be much more effective in catching birds (it of course depends on how well/fast the cats can fly). Probably the number of birds would be considerably reduced. I can imagine that this would give cats a much worse image, with some people even turning to hunting cats (at least those with actual flying capability, that is, without their wings clipped) in order to save the birds.
Note that there is always a certain population of stray cats who obviously would not have their flight disabled; moreover, flying cats are harder to kept from escaping (just like birds, they might just fly out of your window when you open it), so the number of stray cats would probably also increase. There would probably also be a number of cat owners who would outright refuse to disable their cat's flying capability or to lock them in.
Continuing with ecology, a reduced bird population would likely result in an increased insect population, both of insects that damage plants or bite animals and humans, and of insects that are just annoying.
A flying cat, being now able to eat more birds, might in turn kill less mice and rats. I don't know how large the effect on mice and rats is currently (I guess most pet cats won't be hunting mice, but will be fed exclusively, but on more rural areas, cats will more likely kill mice and rats, and of course there are always the stray cats.
So assuming cats play a major role in controlling the population size of mice and rats, them hunting less mice and rats would possibly cause a mouse/rat pest.
About the social effects: Of course, cats developing wings in a very short time frame would in itself cause fear, for the simple fact that this is unexpected, and I would assume also unexplained (at least at first). If cats can suddenly acquire flight, then who knows what sudden unexpected changes other animals, let alone humans, might experience soon? There would probably be a hysteria where people watch animals as well as themselves/each other, and panic over anything unusual (or usual which they didn't notice before), fearing it is a sign of another sudden change, possible for the worse. Hypothetical scenarios of giant man-eating rats or similar would probably be painted in certain newspapers. The wildest theories about the causes would also circulate, from government conspiracy to aliens trying to take over the world, from an action by god to punish the faith-lacking humans to blaming it on the radiation of nuclear reactors or genetically modified cat food.