I think they were also hoping to get some eyeballs on their brand name by having people check in for the points, and having all of their friends see the check in. Having your friend check in at Holiday Inn more often than usual means that the hotel gets (almost) free advertising, and also implies that your social network friends are fans of the brand.

However, with either goal, I never understood what UA/CO stood to gain by just having people check in at an airport.

I was always worried about going overboard and getting my account shut down, so I took it slower than many people here and made sure the check ins looked as realistic as possible, but still managed to pull in almost 10k points total over the three programs I was targeting. Not bad for a few seconds a day.