So I have a client that is primarily a waterfall shop (at least in the team I'm working with). I was actually surprised because this isn't some low-tech organization but a Silicon Valley tech company; I was expecting agile to be part of their project methodology but they pretty much follow waterfall.
When I started digging into how they run projects, I came across some interesting information. They spend a fair amount of time up front gathering requirements, so I was thinking if requirements are stable, maybe this is ok. But when I asked about changes, they indicated they do have a fair amount of changes once the business owner sees what is being developed. Add to this projects that are taking longer than they want and a lot of time testing and fixing bugs after coding is done.
If this isn't a classic need for agile! They said that they had tried agile before but it hadn't really worked. However, as I talked about some of the benefits of agile, they seemed willing to try. So now I'm working on setting up a pilot project to test an agile approach.
There are a number of reasons an agile implementation can go wrong. It needs executive support, the team needs the proper training, project managers need to accept their new role. We'll see how things go here, but I'm optimistic. Having been in consulting for some time, I can usually sense if my recommendations are going to be implemented or if things will go back to status quo after I leave.