I couldn't find any other posts about this topic; please forgive me if I'm rehashing an old discussion here.
I finally got in a decent amount of game play with DA tonight. It's blowing me away so far! (Me, not my empire; that's doing all right, thank you).
On a lark I tried putting an agent on an Altarian Refuge planets' farm tile. 'It can't do what I think it can do,' I said to myself as I placed the agent. The planet (Iversonia something-or-other) had one basic farm and a population of 9 billion. The agent was placed and I hit the Turn button.
When my next turn started, the agent was still there, the farm tile had the red border, and the planet's population was 6 billion.

!!! 3 billion people killed in one turn just by espionage!
To add insult to injury, that same turn, I removed the agent from that planet and dropped him on another planet's farm. Next turn, that planet too was down to 6 billion population.
Even if this is working exactly as intended, it seems to me like a
huge exploit waiting to happen. Imagine training up a bunch of agents and saving them until you're ready to invade some planets. The turn before your transports lumber into orbit, SHAZAM! you've decimated the defenders before your invasion starts.
Am I missing something here?