I agree with Thin Albert. Perhaps we could keep the Wannabe's free of charge so the usefulness of Pprune wouldn't be denied to whoever wish to enter the industry but I would also agree with a more restricted access to the other forums (fori??), where Professionals (aviation and aerospace related) could gather.
I would gladly pay my membership to make up for the potential loss of income coming from advertising. Then again if it wasn't enough, perhpaps leave Pprune the way it is, with its vast audience and let's have some sort of "Professionals" forum with restricted access.
Seems always easier than it is anyway
Have a good week end all