One of the biggest risk to any IT project is change. The more changes you get during a project, the more difficult it is to deliver it on time and on budget. Letting change happen willy nilly is a bit like going to a bar and asking the barman for a white wine. Then when he's about to pour it, change your mind and ask for a red wine. And when he's about to pour the red wine, change your mind again and ask for a beer: any sensible barman will then stop and ask you to make your mind up before going any further, potentially charging you if you changed your mind after the drink was poured. It's also a sure way to get served very slowly.
IT projects are the same: if you keep changing your mind, you will never deliver and if you change your mind too late in the process, it's going to cost you a lot. This is why a good Change Control Process is essential.
Now, the project I currently work on has had every single aspect of it changed over the past three weeks. I cannot name a single thing that is identical to what it was three weeks ago. We even changed the Change Control Process!
In fact, I'm unfair, there is one thing that hasn't changed: we are still working out of the same floor in the same office. But that's because we're only meant to move offices in October.