Comcast is bringing data caps to a bunch of new cities beginning November 1, roughly doubling the number of markets where it imposes data limits and overage fees. As before, customers will be allowed to use 1TB of data per month before being hit with overage charges of $10 for each additional 50GB. For an extra $50 per month, customers can purchase unlimited data.

Prior to the expansion, Comcast said it was enforcing data caps in 14 percent of the markets in its 39-state territory. Instead of immediately imposing caps nationwide, Comcast has been steadily rolling them out to new markets since 2012, usually adding a few at a time and gauging customer feedback before expanding to more. The caps were originally 300GB a month, but as more customers started exceeding them, they were boosted to 1TB (downloads and uploads combined) this year. Comcast says more than 99 percent of its customers use less than a terabyte of data.

Markets in 18 states will face data caps and overage fees for the first time, though other markets in some of these states were already capped.

Here are the newly capped areas, according to a Comcast FAQ: Alabama (Dothan); California; Colorado; Florida (North Florida, Southwest Florida and West Palm); Southeastern Georgia; Idaho; Indiana (Indianapolis and Central Indiana, Fort Wayne and Eastern Indiana); Kansas; Michigan (Grand Rapids/Lansing, Detroit, and Eastern Michigan); Minnesota; Missouri; New Mexico; Western Ohio; Oregon; Texas (Houston); Utah; Washington; and Wisconsin.

Comcast's data caps already existed in these markets: Alabama (excluding Dothan); Arizona; Arkansas; Florida (Fort Lauderdale, the Keys, and Miami); Georgia (excluding Southeastern Georgia); Illinois; Northern Indiana; Kentucky; Louisiana; Maine; Southwestern Michigan; Mississippi; Tennessee; Eastern Texas; South Carolina; and Southwest Virginia.

Customers can exceed the cap in two "courtesy months" each year before overage charges kick in. "This means that you will only be subject to overage charges if you use more than a terabyte for a third time in a 12-month period," Comcast said.

Comcast once again justified its data caps, saying in a blog post yesterday that the "data plans are based on a principle of fairness. Those who use more Internet data, pay more. And those who use less Internet data, pay less."

In reality, paying "less" actually means paying the same amount as before unless you choose a "Flexible Data Option" that provides a $5 discount if you use less than 6GB of data in a month. That discount comes with the risk of racking up overage fees much faster than the standard terabyte plan and thus isn't advisable unless you really use very little data each month.

The caps themselves are a "business policy" rather than a technical necessity, a Comcast engineering vice president acknowledged last year. Unfortunately, Comcast's data meter hasn't always been accurate, and Comcast has been reluctant to acknowledge any problems except when customers contact the media.