Is not a big news to know that I.T. companies have problems with methodologies. They want them but for some reason they fail implement them, of course this don't prevent a big logo with CMMi, ITIL, RUP, XP, Scrum, ICONIX and etc to popup in your face. Jut hire some experts to give some presentations, put some docs and fancy names for these and you are ready.
The impression I got is that competition and "everybody says is great" is the most compelling reason for this kind of behavior. A company should improve always so get some methodology is a improvement, get two is more improvement, mix the best of the two is better! Well, not. One big company said to me that they have a "kind of CMMi" they extracted some steps and used only what was the best about CMMi. What is the problem with get the best of? The problem is that there's no such thing as the best part of a methodology, you can't decide this, you shouldn't decide this.
Take religion, have you heard some people saying that they are Spiritualist, Catholic, Buddhist, Muslin and so on? That they think that some concepts of one religion are great but others not. Ok, everybody should analyze, think about, take conclusions but they have to remember that not all aspects are in our comfort zone. If you want to call your self a Buddhist you should remember that implies not to drink beer. And this is not a silly rule that some monks thought about, there's a reason for it and sometimes you can't see the point.
What I trying to say is that, companies are very naive thinking that they can point out what to adopt or not. The CMMi, as a example, is well thought and every aspect is there for some reason. When you try to decide what is the best for you is it certain that your comfort zone will drag you to rules and procedures that favors your zone, that's the big and real problem.
Do not try to mix to make it best just stick with one, if is not working try another, and another, but the mix don't improve your results, in fact can lead you to a false perception that methodologies do not work. I know that there's no perfect solution and after you have a methodology then you can tweak it around to fit your needs.
"Simplicity is the shortest path between two points" - Bruce Lee.