Law professors and amicus briefs are very much a part of the litigation industry. A recent example is here from am amicus brief on ATS issues. Now, here’s this new Opinio Juris post/essay with thoughts from a larger article on when and how law professors should or should not participate in amicus briefs. The post includes links to other related writings and blog posts. 

Further questions also can be raised. Should amicus briefs be viewed as "sponsored research?"  Should there be disclosure of all past and current economic interests?