I'm just brain storming here.
I thought that only allowing sustaining members to create threads would be a good way to keep people from spamming on the forum. A lot of people come here just to plug their projects and then they dip out, or barely post in other topics. Remember that non-sustaining members could still post in threads, just not create them. Simply making a thread called "Castlevania News and Rumors" would create an outlet for non sustaining members to post their info. So really, nothing would be lost. I feel like this would keep the unwanted material out more than it would keep the wanted material from getting in.
Of course donations would be on a volunteer basis only. But that doesn't mean that the forum shouldn't give a member some sort of incentive or appreciation for making a donation. I think at very least, sustaining members should get an award as a thank you for their investment. That's only being polite.
But again, I'm just brain storming!