I’ve worked on a lot of DLP projects in big enterprise, and I have a very dim view of the entire category of product. A lot of their functionality is just magic black boxes, that unsurprisingly achieve very little. The primary motive for deploying them is not that they’re particularly effective, it’s so that you can tell auditors and other scrutineers that you’ve got a “DLP solution”. The idea that you can grant people access to huge quantities information, but then very strictly control what they do with it is fundamentally flawed. Especially on networks that require large amounts of in and outflow for BAU. Even the most tightly controlled data in the world cannot be protected from an inside leaker (or adversary who has taken control of an insiders access), because it runs into the same “analog hole” issue that DRM products have.
