It is possible to method to create custom usergroups in joomla
I am afraid which i found the solution myself. You have to use a component like NoixACL. Or we will need to wait until joomla v1.6
Thanks for everything Morchot
Have a look at Community Builder, that's the one which everybody uses.
There is an excellent ACL ingredient that i made use of on the site some time back that integrated nicely with paypal
there is a great horizontal user control system that simply combines with joomla