I've been noticing lately that a lot of the newer GSM phones are
> starting to do this. I worry that GSM handset manufacturers are
> starting to get a little bit careless in taking steps to avoid
> interference.
Nonsense. GSM phones have always done this. I think you're stating this because GSM has become more mainstream than it was several years ago.
You will find, however, that CDMA based phones (those on Verizon,
> Sprint, Alltel and a few others) will not have this problem.
That's because CDMA uses a different scheme to communicate with the system than does TDMA and GSM.
Just because it's cellular does not mean everything works exactly the same way from different system to different system.