"It is time to speak honestly about the gap between our intentions to build working systems and our ability to do so in practice. This gap is typically not caused by a lack of effort on behalf of developers or users, but rather is the result of misdirected efforts. The systems development and implementation process will continue to be overly challenging if we work against the tide by trying to make users fit our theories of how and when they should participate in development initiatives. Instead, we suggest catching waves with users at opportune moments, working to hear what they are saying, and then adjusting our, and their, expectations about when a system is completed." (p. 55)
As the authors say, it's not a matter of not including and involving users -- that has to be done. My own design practices revolve around it. What it's saying is that doing so is not a panacea and does not in and of itself guarantee you any special insight or improved chance at success. You still have to interpret, be flexible, do different things at different times, improvise and make sense of what you are hearing, how you are listening, what the users themselves can and do pay attention to, etc. Doing so is also an ethical stance for design practitioners -- no matter how good, they aren't going to know and perfectly understand in advance what user input means and what has to be done.
The article is Wagner, E. L. & Piccoli, G. (2007), 'Moving beyond user participation to achieve successful IS design', Communications of the ACM 50(12); pp.51-55.