It is not just Facebook and LinkedIn. I've seen this from random small sites.
Some other silly shit that come to mind - having the unsubscribe link after half/full page of white space, once you click on unsubscribe "give us 24 to 48 hours to remove your email" etc. Really? they need 24 hours to delete (or change a flag) in the database?
Sometimes it’s some freaky ETL script that runs daily to put your address in a marketing message integration system. Not that it’s a great excuse, just usually more than a single flag update.
Some other silly shit that come to mind - having the unsubscribe link after half/full page of white space, once you click on unsubscribe "give us 24 to 48 hours to remove your email" etc. Really? they need 24 hours to delete (or change a flag) in the database?