Instructions from PDF of HTC Droid Eris (running Android):
Contact with the antenna area may impair call quality and cause your device to operate at a higher power level than needed. Avoiding contact with the antenna area when the phone is IN USE optimizes the antenna performance
And:
…and remove the device from your pants’ pocket before sitting down. It is also recommended that you store the device in a protective case…
Antennagate is contagious.