A lot of things keep AT&T CEO Randall Stephenson up at night. If he has enough hair gel to get through the week… Putting down the pesky rebels led by that Luke kid from Tatooine. But mostly it’s about how third-party messaging systems are taking money out of his company’s coffers and how he never foresaw that people might actually want to use smartphones for things other than checking e-mail.

Speaking last week at the Milken Institute’s Global Conference, Darth Stephenson looked back over his days aboard the Death Star and said, “My only regret was how we introduced pricing in the beginning, because how did we introduce pricing? Thirty dollars and you get all you can eat… [I]t’s a variable cost model. Every additional megabyte you use in this network, I have to invest capital.”

Of course, since studies like one done by our pals at Consumer Reports show that most smartphone customers, even those with unlimited plans, are only using a few hundred MB every month, what Stephenson is really saying is that AT&T could be bleeding heavy data users dry rather than trying to throttle their data after if it reaches a completely arbitrary level each billing cycle.

And then there’s texting — or rather the fact that some people are doing less of it thanks to third-party apps like Facebook Messenger and iMessage that use data connections to transmit messages instead of a customer’s text plan.

“You lie awake at night worrying about what is that which will disrupt your business model,” sighed Randy. “Apple iMessage is a classic example. If you’re using iMessage, you’re not using one of our messaging services, right? That’s disruptive to our messaging revenue stream.”

And if you’re doing this messaging while your smartphone is connected to a WiFi network, you’re not even chewing away at your tiered data plan. This means that you are depriving AT&T of the precious overage fees it desires.

AT&T Chief Regrets Offering Unlimited Data for iPhone [NY Times]