In my experience, people get very enthusiastic about Agile and they start working Agile. Then the frustration comes: Why don't the other guys understand that Agile is the perfect way of working? This is often the case when a small group starts adapting Agile, and they still have to do with "the other guys"... For example: the Business. The Business heard that Agile is fantastic and that you really should be Agile and that it will create value for them. Only; why won't anybody tell me how much things cost? Where is my estimation? When will it be ready? What's this thing about flexible scope?
In my opinion, this illustrates how important it is to guide a company when implementing Agile. Not only it gives the developers a chance to do the right things and get used to it (get velocity) but it makes clear to the business it's not just some methodology, but a mindset, the Agile Mindset. And it will save both parties, and others from quite some frustration.