I just received my new 70-200 f2.8 IS II a few weeks ago and put on a Hoya filter I had been using on my 24-105. Well, the other day, the 70-200 fell off the table onto the hardwood floor. I heard glass break and was fearing my $1900 investment was just ruined. Luckily, it was just the filter. I thought I had escaped damage but after gently cleaning out the glass, I noticed there are now some scratches on the front element. If I had not had a UV filter on there, the lens would have been undamaged. I think I'm going to reserve filters for situations where I'm shooting in dirty, dusty, sandy, snowy or rainy conditions but leave them off until then.
Isn't that a bit like throwing out the baby with the bathwater? That's a really unfortunate drop, but only carelessness would have let your lens roll off the table. I shoot most days of the year in all sorts of physical environments and experience has taught me that when push comes to shove, UV or protective filters are a good idea, primarily for their protective function. I've smashed filters in biffs that would have either damaged the front element, or at the very least damaged the filter thread. I'm always with a hood for the same reason. They make great shock absorbers.
Filters also offer the real-world option of cleaning the dust/dirt/water/smear/sludge that will inevitably land on the front element from time to time with your t-shirt, tie, facial tissue, spare sock or whatever without having an anxiety attack about damaging the front element. Give it a good quick scrub and keep shooting.
I routinely replace the UV/protective filters every 3-4 years or sooner if they're showing that unmistakable patina of fine scratches.