The ends do not justify the means, if you want the buy-in of your people.
There is a school of thought that it is better to ask forgiveness than permission, and I am sure there are times when that is the best approach. However, working through the process with the front line employees, the middle management and senior management builds ownership and commitment. When everyone understands the goals and sees how this change will benefit them, they will fix whatever does not work as planned. If the change ‘happened to them’ they will complain about whatever does not go as planned and leave it to the implementer to fix. And worse, they may take any opportunity to bad mouth the change.
Its a lot harder to convince people to do something than it is to tell them to do something. It takes patience and great listening and understanding skills. But, often times those that are hard to get onboard offer the most valuable insight and can sometimes avert disaster.
Of course, there are those that cannot be convinced. There are a long list of reasons that someone may never get on board and, as trite as it sounds, how you treat them is just as important as how you treat those that do get on board.