While looking at new players in the DLP space, I ran into Illumant. They have two interesting documents for downloads if you are in the market for DLP: http://illumant.com/Global/Solutions/DLP.php?gclid=CO6atfmJipgCFRsRagodRAO_DQ. There is both a white paper describing what should be considered when evaluating DLP vendors, as well as a matrix of vendors and their capabilities. The white paper could have been much more in depth, but is a good overview before starting to look in earnest. Both Forrester and Gartner provides a much more in depth coverage, and it is well worth the investment to purchase both companies' reports prior to investing in a DLP product.