I agree with most of the posters. 23 is by no means too young to know better. Many people have responsible jobs, homes, mortgages and children by that age.
The US have been cracking down (or trying to) massively on online piracy in the last few years, it's well known and if he still ran a website that 'acted as a google search engine for links to piracy websites' then he must have known the risks and judged them worth taking. Makes no odds that his site didn't actually host any pirated material.
He strikes me as an arrogant individual who, now the shit's hit the fan, has to get Mummy to fight his corner. The US has every right to extradite him and the UK seems to agree. His mother's claim that the extradition order was only upheld by the court because the judge didn't have the technical knowledge to properly understand the case is hugely arrogant in it's self.
And don't pull the whole 'he didn't know this was a crime in the US' shite. Ignorance is no defence.