Here are a few that I don't think anyone will mind seeing publicly listed:

- Tons of Americans have joined BA in the past 3 years because of the big Chase promotions. And as everyone knows, actually *flying* BA is about the worst thing you can do with Avios. You get across the Atlantic on EI, RJ, or someone else. You fly short-haul nonstops in the U.S. on AA. You maybe go Far East... Anything but BA, thanks to the YQ.

- Years ago, everybody joined Amtrak because it was a "lossless" transfer between a couple different programs. Amtrak has since added some activity requirements related to transfers so I don't think people do this anymore.

- Lots of people join Starwood solely for the 1.25 miles/$ on the credit card into a bunch of different airline programs. I'm sure Starwood is quite happy for people to do this, although once you figure out how valuable Starpoints can be at the hotels, you might not transfer the points anymore. It's a pretty good hotel program overall...if SPG brings people in via the Amex, good for them...

- ANA has already been mentioned but the utility of that isn't what it once was. For one, there are some other good award search tools out there. Two, UA's site has mostly caught up in terms of showing *A award options. If you need to do something complicated, something like Award Nexus will help. If you just want to look at partner availability for things that aren't too unusual, United.com is probably good enough.

- I've known several people who've joined US solely to participate in a Grand Slam. I also know one guy who decided to fly them for one R/T, got upgraded both ways on his Silver Trial, and ended up switching over to them for good. He was originally there for the promo miles...ended up becoming an actual frequent customer.