What are the Disadvantages with Cash Flow Forecasts?

-Sales can be Lower than Expected, and this can be because your Market Research had Issues, or your just too Over-Optimistic -Customers may not Pay on Time; meaning Cash won't be Received then -Cost of Production may be Higher; Cash Outflows is Higher. This can be because the Equipment is too High, or its too Inefficient -Some Costs may not even be Listed, which may be very Detrimental