Alright this is my question , If you start your forum on a host such as forumotion is it worth it in the long haul? I know you could still get money off of ads and such .. that seem like a win/win.. But then again the server isn't garuanteed to stay up.. You could always switch from free host to your own domain and host .. Or should forum creators just go right for the domain and host?

You could use a service such as Ning that allows you to start a forum and social network for free and then you can pay for premium services when your site gets to that point.

Starting a forum is tough so there is no shame in testing a few ideas and learning the ropes on a free service. Once you understand what you are doing you will probably have a better idea for a new forum and that could be the one you invest more money into up front.

I agree - free or freemium platforms allow you to test ideas/tactics out and when your community grows, you can migrate the community.
A word of advice on growing any online community is that your need to obtain a critical mass/membership and keep them coming/engaged.