If it seems like this is the season when every ISP out there is messing with its data caps, well, that’s because it is. Up today: AT&T, with its second shift in data cap policy in the last six months.

In a corporate blog post today, AT&T announced increased data for its higher-speed customers… but not for anyone stuck on DSL.

AT&T’s GigaPower customers — those pulling 1 Gbps fiber speeds in a few select markets — no longer are subject to a data cap, and can pull unlimited data. Meanwhile Uverse customers getting connections of up to 300 Mbps will see their data cap bumped up to 1 TB from its current limit of 300-600 GB. And, like everyone else, they’re now offering an add-on for unlimited data, to the tune of $30 per month.

It’s actually only been a couple of months since the last time AT&T updated their data cap policy, back in March. But since then, everyone else has been tweaking their own policies, so AT&T may as well shift to be part of the club.

Charter agreed not to impose data caps for several years as a condition of being able to merge with Bright House Networks and Time Warner Cable.

Comcast expanded how many cities are subject to data caps, but also expanded their data cap in all markets to 1 TB per month and added a $50 “unlimited” tier for customers to buy.

CenturyLink, likewise, started charging their customers up to $50 per month for exceeding the data caps on their service.

So why, other than keeping up with the competition, is AT&T making another change just four months after its last big shift?

Part of the answer is in its own blog post: our old friend, corporate synergy. AT&T’s offering unlimited data to anyone who signs up for both Uverse internet and also either Uverse or DirecTV TV service. In short, now that it can match other providers’ double-play offerings more widely, it’s sure as heck going to — and it’s going to try to give users incentives to go for it.

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