Recently, mobile Internet providers (mine is o2, here's some of their thoughts here) have been blocking access to particular websites deemed suitable only for the over 18s. Needless to say, regulators are being blamed. However the lack of consultation, prior warning and indeed complete randomness of sites that are banned (I can get IC, but can't search for latex tentacle dresses) is entirely the bag of the service providers, not their regulators. Also, the regulator in question is funded by the mobile companies, so we can put the problem squarely back at their door. You broke it, you bought it, o2.
The reason for this? Someone wanted to think of the children. It seems that parents are getting contract phones for their children, so rather than setting up parental controls on those phones, all phones need parental controls. Now, aside from the fact that this is rather like me buying a dog and expecting everyone else to walk it, as an argument it seems a little like, well, bullshit.
There's a good article here on bitterwallet.com which touches on some of the problems caused by this decision. The key one being that the remit of the IMCB means there is absolutely no way of ensuring that parental controls could actually stop children from seeing any "inappropriate content".
Let's also take a moment to consider the phrase "inappropriate content". It is almost certain that you and I are thinking about different things and indeed there is a general lack of any consistency in terns of what is and isn't appropriate, even before I lament the grammatical failure of the phrase (if I'm googling porn, and get porn, I'd consider that pretty appropriate).
Sadly, a lot of the sites that are blocked are educational, specifically sex education. Exactly the sorts of sites that young people need access to. There's a good article here on the problem with how mobile censorship (doesn't) work and how it often restricts access to useful areas (like sex education) but allows "family friendly" boobs-out images, such as appear in The Sun. This means that not only is this censorship not working, it is actively working against that which it purports to do: look after children.
So, if you have a spare few minutes today, I'd suggest you shout at your mobile phone company. Then email them.