August Aurelius,
The feature Yankee is talking about was removed.
There are still several ways to earn Gold Coins in-game. These include, winning the monthly awards for having a high score with your country or enterprise, achieving a game level you haven't reached before, and achieving a war level you haven't reached before.
Otherwise, Gold coins can be purchased with real-life money, and are given as a bonus when you extend your membership by several months in a single payment.