Keith, I hate to see things change, but clearly they must. I say why not make some changes now:

- add advertising for non-contributors. I know you don't like it and I know you feel that you promised us you wouldn't do it, but frankly you only promised it if there were contributions.
- add a "nag" screen for non-contributors, if that can be done easily.
- make some forums read-only to non-contributors
- turn off image posting by non-contributors which should cut bandwith and/or increase contribution
- automate contributions, if that can be done with a vBulletin add-in relatively easily.
- black out the forum for non-contribtors occasionally to remind them what a great thing they are missing.

I'm concerned about turning off the search resulting in an increase in posts that wouldn't have been made if the search was there.