At my university and many others in Georgia, retired faculty are allowed to continue teaching and receive some salary after they begin taking their pensions. For many universities, this has been an excellent mechanism to maintain academic standards in spite of belt tightening by state government. Some abuses have occurred, however, and the policy has come under attack recently in both Florida and Massachusetts.
I fear that the cures being proposed for the abuses will be worse than the disease. On the other hand, I would like to see universities hiring young dynamic faculty rather than making do with dead wood who are trying to supplement their pensions. On balance, I believe that most educators are in this business to impart knowledge. The "double-dipping" that I know about provides senior faculty with a mere pittance of what they made as full-time tenured faculty. We are lucky to have most of them around. At Valdosta State University, in particular, they provide continuity and enhance the university's reputation for quality undergraduate teaching.