Exactly ^^^ I've experienced this firsthand between my home in El Paso, TX (weak signal area), and a relatives home in NE Pennsylvania. For the longest time I figured people had to be lying about their battery life as mine has been terrible at home. Additionally, Every time someone would post a pic of their battery screen the only things displayed were service related components so that led me to believe they aren't using them like they say they are.
Anyways, the above poster hit it on the head; the weaker the area, the harder your phone will scan and scan to find a better signal. Thus, eating that battery life faster than you'd like.
Sent from my DROID RAZR