ClickZ's Rebecca Lieb posted a nice, brief, article today on the paid content business model. Instead of just talking about the fact that requiring paids reduces your traffic (something that so many other commentators are shocked and worried by for reasons that have always escaped me), she discusses whether this means you can raise your ad rates because paid content buyers are more qualified. And she slips in a mention of CRM issues that many newbie paid publishers forget to add to their budgets.
Personally I believe the online paid content world will begin to greatly reflect the offline paid content world. There will be audited circulation sites in niches that folks will pay a lot to advertise in, there will be lower priced paid sites in big niches that folks will pay even more to advertise in, and there will be higher priced paid sites in little niches that won't carry any outside ads. There is very little that's new under the sun.