Before this change, countries did not lose PM units if they dropped land. This could be abused in the following way:

A theo buys a small amount of military tech and stays logged out for the last 450 turns on the express server. It logs in during the final five minutes (so there isn't any additional PM decay) and plays nearly all of its turns. On its final few turns it builds military bases. It then drops all land but the military bases. The country can now purchase 450 turns worth of units at full TMBR prices for very little cost. The only cost is the minimal amount of military tech and the destruction costs of the buildings.

The severity of potential abuse was dependent on the length of the round and whether or not the two billion bug is in place. In ffa, it was possible for it to be exploited very heavily. To my knowledge, it was not. However, because we consider this to be an exploit, it was patched immediately on all servers. From now on, if you drop acres your private market immediately shrinks proportionally.

I'd like to extent a big thank you to the player who reported this to us.