Ummmmmm why not? If you can get two, or three, or four, why not! I love my FZ8, but I also like my chopped vstar, and the XR650 is a lot of fun. Now i am tinkering on a Kawasaki ZR7, its just fun to ride different bikes. And the 8 doesn't do it all, I could never take my 8 through the trees when I am cutting through because traffic sucks! Most people I know that have more than one, have a touring bike, a commuter, a track, and another either something like their first bike and its sentimental, or something they are building.
DJ