City given to team-mate gets for free two units

It's a major balance problem for team games. You can give city to your teammate (it's ok), but it generates for free two units (depending on game era: Warrior, Axe, Maceman etc.).

Your teamate can give you this city back - another two units, you can give it to him - another two units etc etc...

Firaxis, please fix that! It's very hard to trace and it make internet team gaming very hard (you have to trust your opponents that they will not use this exploit).

I did this to my enemy, gave him back all his cities that I had taken, and I had assumed that it was like "Drafted" units, that is the city takes a unhappy hit.

I didnt look, but if you have a save, look see if they are taking a "drafted" unit penelty

Anyone will confirm it and put on the consolidated list? It is serious problem - by gifting city back and forth one can generate infinite count of units there is no way to check until the and of the game, when reply is played...
Additionally sometimes it is very needed to give cities to your team-mates (to use trait bonuses to build units or to build special buildings like Vikings lighthouse etc.).
So it would be nice if Firaxis would patch it...