Don, Jun, Andrew, I'm not criticizing the acs_objects model based on this book, but based on my 1.5 years experience with an OpenACS-backed site with 20.000+ users, about 300.000 objects (without acs_rels!!) and a peak load of up to 120 concurrent accesses.
OpenACS' data model was not good enough for that site!
Basic things in the data model had to be changed. Some of these changes were rather light i. e. adding semantics to acs_objects via two tables acs_objects_description and acs_content_areas was not that worrysome.
