Two years after the original post, I'm still wondering why so few companies that collect birth dates at sign-up send a simple note on their customers' birthdays. Of everything I'm subscribed to with my personal and test email accounts, only Cirque du Soleil and OkCupid are doing something on this unique and, I bet, high-open-rate day. I haven't seen any company with a page or an app on Facebook doing anything either.
Chad White of the Retail Email Blog that tracks over 100 retail email campaigns commented that "birthday emails are rare among retailers as well". Is there a cultural reason behind this that I am missing?