At this moment the game allows you to forcefully overpopulate a planet and thereby generate more production, research and/or wealth on that planet than otherwise possible. Since the overpopulation-death-rate for a planet is a fixed 0.1 pop per turn the workforce does not diminish rapidly. These two facts give rise to the following 'cheat' /strategy:
1) have a large planet generate lots of population: Birthing subsidies;
2) conquer/colonize a planet, and overpopulate it;
3) build up the planet really fast, even when you don't have the wealth to buy improvements, by building an improvement every turn;
4) when the planet is fully operational, move the 'excess' population to the next planet;
5) rinse and repeat.
When you use this strategy to take a planet near (on in) the enemies territory and then fill it with culture improvements, the enemy planets (culture) flip faster than a street hustler card trick. I play tested this and without invading a single planet was able to completely culture flip a small galaxy with 3 (godlike) adversaries well under a 100 turns.
The solution would be to either disallow colonizers and transporters to unload more people than the maximum population limit onto a planet or kill the overpopulation really fast (think of it as starvation).
In another of my threads i have proposed such an overpopulation-death-formula.