Here's how Clay Johnson, head of Sunlight Labs, described the need for this project:

Because of politics and scale there's only so much the government is going to be able to do. There are legal hurdles and boundaries the government can't cross that we can. For instance: there's no legislative or judicial branch data inside Data.gov and while Data.gov links off to state data catalogs, entries aren't in the same place or format as the rest of the catalog. Community documentation and collaboration are virtual impossibilities because of the regulations that impact the way Government interacts with people on the web.

We think we can add value on top of things like Data.gov and the municipal data catalogs by autonomously bringing them into one system, manually curating and adding other data sources and providing features that, well, Government just can't do.

Johnson says the site, which is being developed with publicly visible open source code, will allow users to contribute sets of data, documentation to go along with data and links to places around the web that are using any set of data cataloged. It sounds like a ProgrammableWeb type site for public data.

In addition to government information, Sunlight will also be including derivative data sets, like information from the campaign contribution tracker OpenSecrets. That's something it's very hard to imagine a government website including.

Can Sunlight build a one-stop-shopping destination for public data, and will people make use of that? Time will tell, but it sounds like a very important project.