As a datapoint, I had the RF connector on a Revo pop off and flew it that way for several flights. I had Revo set as coordinator, so it was transmitting. I found it because I was getting strange flight behavior some times and looked for the cause.
With this and other times, I know I have run Revo without antenna at up to 50mw and it still works. Of course, a different clone may use a different RF module and not survive this, but I've found that it's generally tolerant. Of course I always intend to have an antenna on when the transmitter could be on.