Stacey Higginbotham ("Over 60% of US Broadband Subscribers have Data Caps" - here) [pictured] explains that "We’re not fans of ISPs capping broadband here at Gigaom, so we’re keeping a close eye on how those caps evolve and who they affect. Check out our updated list on who’s capping your broadband .. In most cases, the companies implementing caps maintain that 99 or 98 percent of their users don’t go over them and have median usages that range between 12 and 18 GB per month. So here are the top broadband providers in the U.S. and their caps. Last year we included a column for exceptions to the cap, but this year there aren’t any, so we took that column out".
ISPs with no caps: TWC, Verizon, Cablevision, Frontier, Windstream, Fairpoint and Cincinnati Bell. 4 ISPs have overage costs - Comcast (see "Comcast Response to Recent Claims: Higher Base Cap w/Tiered Plans or Overage Fees" - here), AT&T, Suddenlink and MediaCom.
See the full table - "Want to know if your ISP is capping data? Check our updated chart" - here.