Berners-Lee has dismissed Web 2.0 as useless jargon nobody can explain and a set of technology that tries to achieve exactly the same thing as "Web 1.0."
Of course, none of this is new news, but I feel that many people still forget that none of this 2.0 stuff came about by accident. To me, Web 2.0 is just people realising that suddenly, things they were always able to do are now en vogue once more - and if they slap some bevelled edges on everything and add some nice, shiny graphics, bingo: Web 2.0-ified. It's also the realisation that they can peddle these things as real innovations, and rake in the cash from venture capital firms by flogging them as new, clever inventions - and yeah, while some of these things are really innovative, pretty much all of them have been done before in some shape or form, just slightly less elegantly. That's through no fault of their own though, the technology enabling people to realise their ideas has always played catch-up to the ideas themselves for a long, long time.
Don't go mad kids, it's just progress... With a drizzling of paradigm shift for flavour.