Limit the scope of your prototype to a defined business area and complete it in a short timeframe.
Grand designs can go on forever and ever, so do the costs.
Change is the rule, not the exception. New technologies in the past 3 years have dramatically reduced the time, effort and cost to implement a KM application. The Web is an incredible source for good information when you know here to look. The Intranet is a very inexpensive means for distributing intelligence. The costs of storing large volumes of information have dropped dramatically KM needs to be tightly integrated with desktop office suites because that is where the information originates and where it is viewed.