When you buy a new camera with a lens or a new lens and you are buying it from a local shop, they will ask you to buy a UV filter. Often the more experienced and jaded photographer will tell you that this is just a ripoff and you don't need the filter. Yet the salesperson will tell you the story about the time the lens was in a sand storm - dropped or pooped on by a bird and the filter saved the lens! Better to lose a $30 piece of glass rather than a lens worth hundreds. So what is the truth? Answer: they both have a point.
For a person who is buying their first DSLR, a protective filter is probably a good idea. Especially of Children's fingerprints are an issue! :-) But, it should not be a UV filter. The digital sensors on your camera are already protected with a UV blocking filter! If you feel that a protective filter is needed get one of the clear filters that is designed for digital cameras. They are specially coated and are designed to minimize flair and ghosting. And don't get the cheapest. I use B+W filters when I do need one. They are not cheap, but they are not going to affect my pictures as much as that $20 un-coated filter from some no name company.
On the other hand, even a great filter has the potential of affecting the image. After all, it is an additional piece of glass added to a lens that was not originally designed for it. Thus many of the pickier Pros don't even use them. As protection to dropping, a good rigid lens hood will do as good a job - if not better - as a protective filter. However, many of these same pros use Circular Polarizer(CPL) filters a lot and they can doubles as additional protection anyway. So, barring your lens getting licked by your 5 year old, you lens is probably protected just fine by your rigid lens hood.
In the middle of this is the reality that in extreme situations (think a wind storm in a desert), many pros will use a filter. It just makes sense to protect your gear in extreme situations!
So the answer is clear as mud, right? Don't sweat it. When you buy that first camera, get the filter, but make the sales person really happy with you and tell them you want a good clear multi-coated filter designed for DSLRs. Yes it will cost more, but it will be the right piece of equipment! At the same time, get a CPL and you will be thanking me later when the water looks real and hte glare is all but gone... (more on this in another article). And yes, as time goes along, the Protective filter will be used less and less as you learn to care for your equipment properly. So, don't sweat it and let the "experts" argue the nuances of the issue. Do what is necessary for you to enjoy your photography!