The June issue of Patent Information News states that the EPO is in the process of reloading US assignment records into its legal status database. When the project is finished US patents in esp@cenet will be linked to more than six million assignments dating back to 1981. Assignment data has been available for some US docs in esp@cenet, but much of the data was corrupted by technical problems. I assume that this includes all the data available on the USPTO's web assignment database and Cassis ASSIGN, although both give a slightly earlier start date of August 1980.
I'm the librarian for research services in the Engineering and Science Library at Queen's University in Kingston, Ontario. I've been working with patent information since 1991, including seven years at the U.S. Patent and Trademark Office. I believe that the dissemination of patent information is a public good and should be promoted, especially in the education of science and engineering students.