If you aren't focusing on longtail keywords on your paid activity, here is further evidence that you might just be missing more than a little trick......it could in fact be the difference between success and failure.

If you are looking at it purely from an ROI point of view there are usually no downsides, they generally convert at a higher rate, have lower bid cost on PPC and therefore your Cost Per Acquisition will look even better.  

Obviously managing a greater number of keywords increases time but once you have your sets tested and tweaked.