In Code Complete, McConnell outlines the idea of having a change control procedure, to stop the customers from changing the requirements whenever they see fit. In fact one feature of the process is to be heavy enough to dissuade customers from registering changes.
The Rational Unified Process goes for the slightly more neutral term Change Request Management, but the documentation seems to imply the same opinion, that it is the ability to make change requests which must be limited. The issue is that many requests for change in software projects are beneficial, and accepting the change request is not symptomatic of project failure. The most straightforward example is a bug report - this is a change request (please fix this defect) which converts broken software into working software. Similarly, larger changes such as new requirements could convert a broken business case into a working business case; ultimately turning a failed project into a revenue-generator.
In my opinion the various agile methodologies don't address this issue, either assuming that with the customer involved throughout, no large change would ever be necessary, or that the iterations are short enough for changes to be automatically catered for. I'm not convinced; perhaps after the sixth sprint of your content publishing app the customer decides to open a pet store instead.
I humbly suggest that project managers replace the word "control" in their change documentation with "opportunity" - let's accept that we're looking for ways to make better products, not that we need excuses never to edit existing Word files. OMG baseline be damned!