Several years ago, Roger Cicala of LensRentals made a few blog posts where he intimated that buying a UV/protective filter was not necessarily a wise investment in a lot of situations. At the time, lens front elements were relatively inexpensive to replace and high quality filters were costly.
However, many of the higher quality lenses produced over the past 5 years have featured more complex front elements, with the result of Roger feeling compelled to revisit his cost-benefit analysis of UV filter use.
See Roger's recent LensRentals Blog post to see if purchasing a UV filter is a wise decision for you and your lens(es).
B&H carries UV and protective filters.