It would be very valuable for government officials and the public to be able to track the uses of open data sets. Are there sources that currently do this and make the information available to the public? This could be either types of uses or specific examples of uses of the data (e.g, links to applications using the data, links to articles citing the data).
Data.gov has a developer showcase with links to 300+ applications that have been made with their data.
update: As does uk.data.gov (per D Read).
Also, if we get into articles, every NASA mission keeps a list of peer-reviewed publications to justify their continued funding. (eg, SOHO, STEREO). The astronomy community calls them 'telescope bibliographies' and currently has a draft circulating for comment (until 24 June 2013) on Best Practices for Creating a Telescope Bibliography There's also been discussion of ADS building tools for people to manage publication lists, but that's still a ways off.
(disclaimer -- I help to manage the SOHO & STEREO web servers. I also remember seeing a chart of Hubble papers that did/didn't include any PI team members, and a few years into the mission, the rate of publication without a PI overtook those with. It was one of the arguments for opening data, but I'm not having luck putting my hands on that presentation)