Originally posted by séamuis if you drop your camera or lens and it hits the filter you are still likely to damage your lens. other than coloured filters for B&W film I only use a UV filter for dusty, windy or other hazardous environments. I don't see how a filter can protect your lens from damage.
My wife once managed to smash a filter mounted on her 18-55 to smithereens without damaging the lens itself. We have no idea how she did it, though - one day she took the lens out the bag and found it that way. Probably the camera bag took a fall one day and she hadn't checked all her lenses to see if they survived. But she didn't have a lens cap on that lens, either, which surely would have protected the lens just as well as the filter if not better (no danger of shards from the cap scratching the lens).
So, with one smashed filter on an uncapped lens in several decades of combined camera ownership between us, and very few reports on this forum or any other of smashed lenses that a filter would have helped with - I think the actual danger of ruining a lens this way is rather less than people imagine. And given that you should be able to insure all your gear for under $50/year - and that will protect your lens again far more things than a filter (filter don't help with theft, for example, or dropping into a lake), I think there are far better ways of protecting your lens investment. And of course, unlike filters, insurance policies definitely do *not* have any adverse effect on image quality.