Comcast user reports from residents all over Illinois, USA indicate the company has introduced a 1TB data cap on its internet services in the region, which it refers to as a "Terabyte Internet Experience."

The e-mail sent out to customers reads: "We're writing to let you know that we will be trialing a new XFINITY internet data usage plan in your area. Starting August 1, 2016, your monthly XFINITY internet service will include a terabyte data usage plan."
It later goes on to say that if you need more data, there's always the Unlimited Data option, but that it's only relevant to less than 1% of its customers. As well, that less than 1% will remain unlimited for two "courtesy months."
While 1TB is indeed plenty for almost everyone now, the cap is a worry for the future when it might not be.