De-anonymizing UDIDs with OpenFeint →
https://marco.org/2012/09/04/deanonymizing-udids-with-openfeint
People keep asking me what someone could do or find out about you with your iOS device’s UDID. I keep saying, “Not much, if anything.”
But if you’ve ever used OpenFeint — that green promo screen that appears the first time you launch many games promising high-score tracking, etc. — that may not be true, depending on what other information or social connections you’ve given them.