I spend quite a bit of time with enterprises describing the difference in philosophies between classical DLP and Data activity monitoring (DAM).  While it is tempting to think of DAM as a core-level data protection (which it can be and is in fact very efficient at), in reality DAM solves a broader problem around business data governance than just leak prevention. The concept of risk, theft and fraud in DAM are much more elevated and contextual than they are for DLP. My previous posts on this went into some detail on this topic. Check out:
Data Auditing and Protection vs. Data Leak Prevention.

Rich Mogull has succinctly described this in his recent post, Definitions: Content Monitoring and Protection And Application and Database Monitoring and Protection. 

He puts it so well, that I am just copying his words verbatim (he uses the acronym ADMP in place of DAM):

"More on this later, but I'm starting to see the data security market splitting along two lines. One focused on protecting content in user workspaces and productivity applications. It's starting with DLP but moving towards what I call Content Monitoring and Protection.

On the other side of data security is protecting content in business applications- from your web application stack to internal applications and databases. I'm starting to call this Application and Database Monitoring and Protection, and Database Activity Monitoring is where it's starting.

Since we need definitions, here's my first stab for ADMP: "Products that monitor all activity in a business application and database, identify and audit users and content, and, based on central policies, protect data based on content, context, and/or activity."

For CMP, I'm sticking with my DLP definition (DLP is a terrible term, but I'm not going to fight the market): "Products that, based on central policies, identify, monitor, and protect data at rest, in motion, and in use through deep content analysis."

From Rich Mogull, www.securosis.com