Call Australia and ask them how their implementation went, or didnt.
This topic was debated furiousley, and after a couple of revisions was eventually scrapped, or shelved at least.
There were fears about performance, scope creep, and the fact that a filter doesnt actually prevent anything.
Once you filter it off the web, if you can get all of it, you force the content underground. It becomes available only via secure and encrypted means, making it impossible to find without knowing where to look - a filter cant look inside an encrypted data stream without being able to decrypt it. Therefore, and with minimal effort, anyone can still continue to access the same content without fear of being watched. All you need is a VPN to another country.
Scope creep is a particularly worrying one. Once the filter is in place, various groups will all push to have content they dont like added in to it. Australias filter suffered this problem during development. Originally it was purely about blocking access to child porn etc - "protect the children from the big bad Internet." Then it also included protecting copyright material (i.e. blocking pirate p2p etc.) And finally it included enforcing content classification - that is, blocking access to content that has been banned, not classified, or simply refused classification by the Govt.
And then at least for some, performance is another issue. Australia trialled several filtering units before selecting one. Worringly, the boxes were only tested to support 12mbit/sec per user, when numerous ISPs were already offering speed from twice that all the way up to 100mbit - and the Govts own plans to introduce FTTH with speeds ranging up to 100mbit/sec. There was also debate about who was going to bear the cost of purchasing all this gear...
So while the intentions are good, the reality is that its a highly controversial move and very difficult to implement.