I've put some notes below - I was transcribing it for myself and thought I might as well share it. It's only a selection of the talk and I haven't tidied it because they're not my words to edit.
Why is linked data important?
Making the world run better by making this data available. If you know about some data in some government department you often find that, these people, they're very tempted to keep it, to hug your database, you don't want to let it go until you've made a beautiful website for it. ... Who am I to say "don't make a website..." make a beautiful website, but first, give us the unadulterated data. Give us the raw data now.
You have no idea, the number of excuses people come up with to hang onto their data and not give it to you, even though you've paid for it.
Communicating science over the web... the people who are going to solve those are scientists, they have half-formed ideas in their head, but a lot of the state of knowledge of the human race at the moment is in database, currently not sharing. Alzheimer's scientists ... the power of being able ask questions which bridge across different disciplines is really a complete sea-change, it's very, very important. Scientists are totally stymied at the moment, the power of the data that other scientists have collected is locked up, and we need to get it unlocked so we can tackle those huge problems. if I go on like this you'll think [all data from] huge institutions but it's not. [Social networking is data.]
Linked data is about people doing their bit to produce their bit, and it all connecting. That's how linked data works. ... You do your bit, everybody else does theirs. You may not have much data yourself, to put on there, but you know to demand it.
It's not just about the number of places where data comes. It's about connecting it together. When you connect it together you get this power... out of it. It'll only really pay off when everybody else has done it. It's called Linked Data, I want you to make it, I want you to demand it.