It turns out using Pro Sites doesn't work for sub-site owners on Multi-Domains + Domain Mapping sites:

So it looks like I'll have to set up most of my domains as their own separate install. How does that work with Anti-Splog?

Even though I don't have traffic on the sites, will I require a new membership for each domain? Is there anyway to share the single membership across my network of domains with Anti-Splog?