One complaint I hear a lot is that ITIL creates its own bureaucracy and management roles start to proliferate whilst the people who actually GET THINGS DONE find themselves with more and more unproductive jobs to do.
This goes back to the early days of ITIL, in fact to one the earliest ITIL projects at the MoD , led by Ivor Evans. Ivor wanted to use an ITIL approach to breakdown the silos, but found that by trying to build an organizational structure around ITIL he just ended up creating new silos.
That is when it struck Ivor that just because ITIL mentions a role it doesn't mean it has to be undertaken by a dedicated resource. It was a topic addressed as well by the other ITIL pioneering Ivor, Ivor Macfarlane, when he produced the ITIL In Small IT Units guidance - I"TIL In Situ", which I believe is due for an eagerly awaited update soon.
In trying to determine which roles need to be allocated to distinct actors the questions you need to ask are the same as in deciding any other organizational structure:
Do people have the right mix of skills - we can't be experts in everything.
What will be the span of control - we don't want a heavy communications overhead.
Do we need segregation of duties, to use an audit term - personally I want my change manager to have as little personal interest in changes as possible so they remain independent.
What authority does the role have - often too many actors means no one is really in charge.
Can we design the processes around the role to reduce the workload - the more things that are done automatically rather than as an overhead the better.
Can roles be carried out by a committee rather an individual.
If we look at all these questions we often find that we can simplify the organizational structure and don't need as many managers as we first thought