Public Service Announcements are generally used by politicians and media types to promote their political agendas. They involve lots of confusing statistics designed to appear simple.

In the wild world of college radio, a public service announcement (or PSA) or two had to be read at every station id break (every 20 or 30 minutes, I don't remember.) Usually the PSA was for some campus event or local concern. Because it was college, there were a lot of PSAs about stress (avoid it) and suicide (don't do it) and VD (don't get it).

For the most part, the public service announcements were completely innocuous.

• The First Liberties series, with an attorney telling stories of how people's rights were protected by the Constitution and crafty lawyers.
• The Arbor Day Foundation, with a voice-over similar to James Earl Jones, or John Denver singing the tree song.
• Beer producers got together and made a "drink responsibly" PSA that starts out by pointing out the historical significance of beer and why it can be beneficial.
• Batman speaking out against drunk driving.
• McGruff, of course