Thousands of internet users could be hit with hidden charges for downloading TV shows and movies.
By Jim Reed
Newsbeat technology reporter
Most broadband companies limit the amount of data that users can copy from video sites.
Basic deals offer just one gigabyte's worth of data transfer, enough for 90 minutes of full quality video.
The explosive growth of video download sites means that more users are being pushed over that limit.
More people streaming
Online traffic to sites like YouTube and the BBC's iPlayer jumped 178% in February compared with last year, according to the research company Hitwise.
Writers in Hollywood went on strike over royalties on internet downloads
More then two million people have signed up for the BBC's iPlayer service.
Up to half a million shows are now streamed every single day.
But downloading all that extra video can be expensive.
Some broadband customers will have to pay more than £2 for each extra gigabyte of data they use.
One user's experience
Phil Campbell from Barnsley uses video sites like YouTube and the BBC iPlayer.
He contacted Newsbeat after being hit with £50 in download fees.
He said: "It wasn't made clear at all. There was no email, no contact. I found out on a bank statement."
Other internet service providers may slow down connection speeds or even cut users off if they exceed their limits.
A spokesperson from the Internet Service Providers Association told Newsbeat: "If there are too many individuals consuming bandwidth then the service is degraded for everyone.
"Users must make sure that they understand what charges or policies will be applied."