And There's ThisKeith Ganey let me know that the Children's Online Privacy Act includes this provision:
"While children under 13 can legally give out personal information with their parents' permission, many websites altogether disallow underage children from using their services due to the amount of work involved."
So it appears that Nike falls into the "many websites altogether disallow underage children", which is fine, but they need to mention the age restriction before you go through all the steps of creating an account. Or when you put in the birthdate, and it's not in the acceptable range, notify the user. Don't give us some crap error message that doesn't explain anything.