Since you asked, I don't want you to do anything Ian. To be brutally honest, it doesn't bother me whether this site fails or succeeds, that's your concern.
Regarding Facebook, not many users like dealing with the devil, but there ain't many other viable options available, and it's really only as bad or good as users allow it to be. One thing it doesn't do is stifle intelligent, informed, cutting edge debate, and that's good. It superficially fills a huge need for social contact that's missing in society today, and that's an opportunity you can tap into as well. The key, if you ask me, is personal contact...
BTW, if you think honourable intentions ensure wild success, you're dreaming. Don't aim for success either, it's way oversold. Aim for something simple and worthwhile.
To me, it seems like you have to make a clear choice about what you want to achieve. Come up with a guiding principle that directs your purpose for the site. e.g. To enable people with an interest in aviation to connect and share their knowledge and experience for everyone's benefit. That's just an example though. It's gotta be what you want the site to be, then all you have to do is make it be that. Simple, but not easy.
Regardless of what anyone says, it has to be your choice because it's what suits you. If it happens to suit us as well, then that's a bonus.