It highlighted innovative uses of public data, made available by governments and institutions.
It was launched in early 2008 by @seanflannagan and @laurensperber and was directly inspired by Aaron Swartz and his project theinfo.org.
It was Sean and Lauren's first Rails project.
Alas, it is no more.
Check out awesome-public-datasets in its absence. It lists many of the datasets that were featured on Datamob.