Snorbs has spoken a lot of common sense and obviously has more knowledge than the minister who has proposed this.
I completely agree with what Snorbs said.
It's not about getting the "perfect" solution, it's about if one is technically possible in the first place and would provide value for money.
Let's assume you can easily block porn websites. What about bittorrents, newsgroups, IRC, GNUTella networks? Most of you have probably only heard of Bittorrent but the rest are also there and you can easily find porn on there too.
And that's before you factor in simply bypassing UK controls by bouncing your traffic from a non-UK IP (eg. using VPN or a proxy).
Think its hard? Think again. Most kids at my DD(14)'s school will probably be able to tell you how they bypass the filters on their school computers. It's about as hard as typing in "how to bypass school filters" into google. Try it.
It's about as feasible as asking BT to implement technology to stop people from saying the word "bomb" during a conversation.
And as Snorbs said, who do we entrust with coming up with the blocklist? The IWF? They flipping blocked Wikipedia after someone posted an album cover for a Scorpions song. The government? Oh, I can see Wikileaks disappearing quickly.
All these proposal's do is provide the politician's with a good soundbite, load up costs onto the ISP's (which will then pass onto us) and the only ones who are "protected" are those too stupid to use a computer.
Sorry but anyone with a modicum of knowledge of how the Internet works will realise that large scale filtering is simply doomed to failure.