The problem with censorship

I'm a libertarian and believe in small government and less regulation. I also believe that children should be treated as children and adults as adults. This may mean that my views on censorship run contrary to yours.
Some countries are trying to censor the internet, most notably Australia. This article at the Register
http://www.theregister.co.uk/2010/01/28/australian_censors/
highlights how difficult it is to define what is obscene and what is not. Most internet porn sites have a 2257 declaration which states that the person modelling or featuring on the page was over the age of 18 when the pictures or video was taken.
The Australians are getting hot under the collar over models who look younger than their age, or whose breast are small, so as to give the appearance of pubescence.
From the Register's article
"Breasts came under the spotlight a year ago, as Senators Barnaby Joyce and Guy Barnett commenced a campaign against publicly available porn. Rounding up magazines from corner shops and filling stations, Senator Joyce claimed that publications featuring small-breasted women were encouraging paedophilia."



The outcome is that the magazines now only show pictures of large breasted women.
The Register again-
""We are starting to see depictions of women in their late 20s being banned because they have an A cup size. It may be an unintended consequence of the Senator’s actions but they are largely responsible for the sharp increase in breast size in Australian adult magazines of late."

This is ridiculous. Images of some but not all women deemed to be obscene because these women have small breasts and/or look younger than their years. Is the proof of age rule currently in place not sufficient?
What if the girl is a minor but has large breasts and looks older than her birth certificate states? Is that OK then?

It is impossible to impose a one-size-fits all definition of obscenity. Different cultures have differing ages of consent for a start. In the UK it's sixteen. Sixteen year old girls have modelled for Page 3 in the past. I can think of Samantha Fox in the 1980s and Lindsay Dawn Mckenzie in the 90s. Both were well endowed girls, so that's OK then?
In the US they set the age at 18. That seems sensible to me., even if their alcohol laws mean that these girls can't legally drink until they're 21.
You see, it's all nonsense. A girl can be old enough to get married and have sex, but not old enough to have pictures taken of her in the act (even if she's a willing participant). She can work in a strip club but not drink there.

The article goes on to discuss female ejaculation. From then on it descends into farce.  I speak from personal experience that some girls (very few in my limited experience) ejaculate when they achieve orgasm. It's a rare phenomenon that pornographers and their models fake as part of the entertainment.
The censors are trying to ban its depiction. How Victorian is that? Queen Victoria refused to accept that lesbianism existed, but it did and still does.
It's life. Get over it.
The girls who make porn films for a living and who are trading on their youthful looks shouldn't be discriminated on in this way.
If the censors get their way and this material is banned, it will only drive the material underground, and 2257 will go out the window. Then you won't know what you're viewing.

When prohibition was introduced, people drank more, not less. When will these people learn?