I totally agree with this.

>True, but problems with "waterfall" go way beyond that.
>
>It's not just that the business needs change - it's that many clients are simply unable to state all their business requirements and rules in one shot (even if that shot is done over weeks or even months). I sometimes find that client's rules are so 'patched' that a full-blown discovery process uncovers the fact that clients have been inconsistent in their own rules. So sometimes buiding a brand new system uncovers so many of these, that the system becomes a "proof of concept" for their rules. And that process sure as heck can't be neatly determined on some bean-counter's ledger! ;)