@ Nitro: "Youth led by youth" means that a group of 7-12 year olds are lead by people between ca.16-21 and groups of 12-16 year olds are led by themselves, being of course constantly helped, advised and supervised by people older (16-?).
The association I was a member of (or still am a member of - paying but not attending ) has "planing groups". Members of these panels are between 18-30. Only in rare cases these people are still leading an own group of younger scouts. First of all because they are in fact considered "too old" for "field duty" but also because at the age of 18/19 they finish school and attend university, in most cases that means they have to leave their hometowns.
These planing groups are responsible for "scouting education". In seminars they teach younger scouts (12-15 / 15-17) how to be a responsible leader of a group of younger or same age people. There are lessons in law, peadagogy, first aid and scouting-history / rituals.
A possible way through the organisation is: joining with other girls and boys at the age of 7 (young scout), staying in that group with the same, older leader until you are 12/13, becoming a scout then, visit a seminar that will teach you (in a very, very fun way ) how to lead your own group of same age scouts, then until the age of 15/16 you will learn to organize the weekly meetings, an older scout still being around all the time but handing over responsibilty more and more, at the age of 15/16/17, depending on your own development, you can visit another seminar in which again in a very fun way you learn how to lead a group of young scouts (age of 7-12). When you have to leave to go to university or apprenticing you are for time reasons obviously out of the weekly meeting in the afternoon, including leading a group on your own but you can join a planing group to organize camps or tours that are attendend by every member of the scout association of the federal state you are living in/are in the planing committee of or help organize seminars - these things take place in the holidays and on weekends. It's a lot to do and to be able to organize of some kind of camps and tours you need people older than 18/21 - to sign certain contracts, book flights, rent cars etc.
The concept of the association needs permanent evaluation of it's peadagogy and content in general. There has to be public relations work and fundraising. That's what's done in these planing groups - not leading a small, own group of 10 kids but leading the whole association, being a contact person for every groupleader in your section as well as contact person for public relations! Responsibility / competences are sectored in federal states, each federal state has planing groups for "scouts between 7-12", "scouts between 12-16" and "ranger&rover (16-?)" because every age group has different needs.
And there are chairmen. And these people are always over 25, most times doing it for a longer period, some of them are 35. The chairman of the whole association is 39 :-). Don't forget that scout associations are almost always registered associations and need to satisfy legal obligations. These people are scouts who are not involved in the everyday scouting but responsible for financial and legal affairs of the association.
As I already wrote I'm still a member of my scout association but not active anymore. There is the saying "once a scout, always a scout". It's different from any other hobby you can pick up as a young person. It is not the everyday sportsclub you join, it's not just something you do then come home from and forget about. You spent a great deal of time with you fellow scouts, who eventually become your clostest friends. You are away from home and your parents earlier and way more often than other kids you age, you take over responsibility for other people at a young age. Having spent three weeks in Pakistan once and having lost half our equipment on day 9 due to a massive cloudburst and following flood I think it's a fair statement that situations you have to overcome and learn to master are not the average problem that you'd propably have if you'd join a rowing team for example.
I was in a planing group responsible for all scouts between 7-12 and their groupleaders in Schleswig-Holstein, Hamburg & Mecklenburg-Vorpommern (three federal states of Germany). When I was 22, a student at university, I was home on 7 weekends. The rest (45 weekends) I spent on the road, giving seminars, supervising camps, tours, organizing and supervising one great journey to Estonia and of course - touring with my same age fellow scouts.
I was privileged, I know that, because Frazzy is right: it's damn expensive. But it made me what I am today, so it was money well spent
I'm 28 but I know already that when I turn 35 I will still refer to myselve as a scout! It's in my blood and it's actually one of the few things I'm proud of because it does not just happen: you have to really want it and do and give a lot in order to achieve this feeling about yourself.
There are whatever guilds of older scouts (30-???) who are still traveling together and are active in other ways. But they don't lead the actual groups of kids or teenagers. I'm not in one of these guilds and I don't think I'll ever be - I'm a scout at heart.