Bill Burnham: Can your walled (listings) garden be trashed?

VC Bill Burnham’s got a meaty post about the distributed web and how listings and other forms of content are becoming commoditized because the premium service walled gardens can’t monopolize all the data and therefore the business models change as the data goes off. Some of the kickers Burnham suggests to be on the alert for:
Content Availability: “If a Walled Garden is charging to distribute or provide access to data that can now be easily aggregated from “self published” web sites, it is in an increasingly tenuous position.”
Index Affinity: “The more willing a data owner is to make their data available for indexing, the more tenuous the walled garden’s business. ”
Process Simplicity: “… if a garden has a highly simplistic process where it simply displays aggregated information, it is highly vulnerable to search led attacks.”
Most vulnerable to attach under this metric–all listings sites, of course, but Burnham says personals are (still) a little more defensible: “Online dating sites, such as, seem relatively safe from the Google?s of the world in the near term thanks to the lack of index-able content and the need for discretion. The real threat to the online dating sites is coming from the social networking sites which should seize a large piece of the dating market from the current walled gardens over time.”