But what Bret is talking about is less about the semantic web — where all data everywhere is linked together by certain tags and/or infrastructure — and more just about getting access to really useful chunks of information, like mapping data and white pages. Heck, it'd be great to just get all US area codes with related information in a nice, accessible CSV file.
Hard to know if this sort of thing could ever come to pass, given that there are likely far fewer people who would edit a large financial data table than, say, the latest goings-on in American Idol — however, I'd love to see it happen.
In the meantime, ReadWriteWeb has compiled a bunch of data sources that I thought might prove useful to you as well. Some of this stuff was new to me and I look forward to exploring them. The one thing that the article didn't mention was the great publicdata tag archive still happening on Delicious that we talked about many moons ago. Make sure to check that out too if you are looking for some good public data sets.