As I read lots of threads on Flyertalk I often come across mention of this program or that which lots of people join, though they have no intention to fly that airline or stay in that chain's hotels. There are good reasons, such as access to a good, usable website, nice transfer options, advantageous opportunities for partner redemption, status and status match possibilities, readiness for periodic special offers, etc. I thought it might be useful to have a thread pulling these varied ideas together. I have not seen one, but point it out to me if it already exists. What are the programs you've joined, and others should consider, despite the fact you never actually use their facilities, and why?