updated 03:52 pm EDT, Thu June 26, 2014
Carrier offers $50 discounts
[Update: Apple also offering AT&T GoPhone prepaid iPhones as well] As rumored, Apple has begun doing in-store activations of iPhones on prepaid carriers. The first carrier to confirm this is T-Mobile, which is running a related promotional sale. People who buy a new iPhone with a prepaid plan are eligible for a $50 discount, so long as a device is activated in-store, and they sign up for "$50 or $70 worth of service." Shoppers opting for a Simple Choice postpaid plan instead can get a $50 iTunes gift card. T-Mobile hasn't announced an end date for the deals.
Postpaid T-Mobile activations have been an option at Apple Stores for some time, but people wanting to go prepaid were previously forced to buy an unlocked iPhone and activate directly with T-Mobile instead. AT&T has meanwhile was rumored as getting GoPhone prepaid activations in Apple Stores, and this has now been confirmed.
[Updated with AT&T's official statement] "AT&T GoPhone prepaid service is now available in Apple Retail stores. Prepaid service is also available for iPhone 5s, iPhone 5c, iPhone 4S in AT&T and Cricket Wireless stores and online at att.com and at cricketwireless.com."