As the boundaries blur between traditional TV and new ways of watching, such as online and on-demand, problems arise over how shows should be regulated.
How is TV currently regulated in the UK?
Media regulator Ofcom ensures TV and radio audiences are protected in areas such as taste, decency, fairness and privacy. But Ofcom only has control over material broadcast over an analogue or digital TV signal.
YouTube does not allow pornography or violence
The new wave of on-demand services are self-regulated by a group called the Association for Television on Demand, whose code broadly mirrors that of Ofcom.
Online videos are much harder to regulate because anybody anywhere can upload a video to the internet.
But responsible sites have systems for users to tell the administrators about inappropriate material. For example, YouTube does not allow pornography, violence or dangerous or illegal acts.
So is there any legal regulation of online video at all?
In a word, no.
Things that are already illegal in the UK - such as incitement to racial hatred and blasphemy - are still illegal online. But there is so much content created, and most of it comes from other countries, that it is very hard to police any applicable laws.
The European Union is in the process of updating its legislation for audio-visual broadcasts, which will contain safeguards in areas such as protecting children from sex and violence and setting limits on advertising.
This was to have covered all new media, including online video - but has now been scaled back to just cover TV and "TV-like" services such as video-on-demand.
So internet video will remain free of regulations in areas like taste and decency.
What will be covered by the EU regulations?
"If it looks like a TV programme and walks like a TV programme it probably is a TV programme," is the view of UK broadcasting minister Shaun Woodward.
In other words, professionally-made shows on TV or video-on-demand services will be covered by the EU's Television Without Frontiers rules.
The UK government argued against regulating other online video because it did not want to stifle new media industries.
For example, if a European version of YouTube started up, it could be at an instant disadvantage against its rivals in the US, where there are no such regulations.
So how can we protect children from unsuitable programmes if everything is so readily available?
The great advantage of the internet - that so many things are so easily available - can also be a potential disadvantage.
Now the EU has scaled back its plans, there is not likely to be any further restriction on what can and cannot appear in online video.
In the home, parental filters on PCs can block access to unsuitable sites. And sites that want a mainstream audience will continue to regulate themselves - or ask their users to regulate them - by labelling or removing offensive material.
But at the end of the day, it is very difficult to stop anybody watching anything they want if they have the know-how to do so.
What about programmes that are shown after the watershed on TV but are also available online or on demand?
On TV, the 9pm watershed - before which programmes are supposed to be suitable by children - becomes less meaningful when programmes are available at any time from the internet.
When UK broadcasters launch their TV download services over the next few months, shows with explicit content will be marked with a G icon - for guidance - along with text explaining the nature of that content.
Some, such as Channel 4, will require users to be over 18 to sign up to the service in the first place.
BT's forthcoming video-on-demand service BT Vision, meanwhile, will use a film-style rating system. Each user will have a pin number, with the option to restrict access to programmes with ratings such as 12, 15 and 18.