Nicolas Robinson-Garcia et al. have self-archived "Analyzing Data Citation Practices According to the Data Citation Index."
Here's an excerpt:
The findings of this study show that data citation practices are far from common in most research fields. Some differences have been reported on the way researchers cite data: while in the areas of Science and Engineering and Technology data sets were the most cited, in Social Sciences and Arts and Humanities data studies play a greater role. 88.1 percent of the records have received no citations, but some repositories show very low uncitedness rates. While data citation practices are rare in most fields, they have expanded in disciplines such as Crystallography or Genomics. We conclude by emphasizing the role that the DCI could play in encouraging the consistent, standardized citation of research data—a role that would enhance its value as a means of following the research process from data collection to publication.