Aside form safety concerns, which I understand really don't exist, I hate when people complain about cell phone conversations. I hear this crying about installing cell phone antennas int he subways, too.
Let's say you're not he train. Two people are having a conversation. That's two voices back and forth.
Now imagine a cell phone conversation....one voice. It's QUIETER!
I think a lot of the reason that people get annoyed by cell phone conversations is the psychological effect of not being able to hear the full conversation of what someone is talking about, and the jealousy that someone is sitting there bored and alone while someone else is having a fun social time by talking to someone.
I think people just need to get over it and get an i-Pod to distract themselves from listening in on other people's cell phone conversations. Or if they really get that upset, see a doctor.