Harvard and Oxford prof Jonathan Zittrain's Web 2.0 Summit workshop this morning, "Web Two Point No — And You Thought Microsoft Was Bad," hits on something few people think about: All the social-network information and messages flying around Facebook, MySpace and AIM are stored and retrieved through proprietary systems — at the whim of the proprietor, as Zittrain puts it. It's a sharp contrast to the email, Usenet groups and IRC channels of yore, which were generally open networks with many points of access. In this respect, Zittrain sees Facebook as the new Compuserve, a members-only resource. Even its myriad apps are built to the company's programming specs, and Facebook can change the terms of the deal for competitive advantage anytime. Be afraid — be moderately afraid.