@Setanta,
Thanks, that was a good link, at least for me.
My own guess is that people who state they have no religion vary, of course. I figure at least some of them shy away from the word atheist because they think it is too strong, that the word means strong in itself, either strong non believer or strong belief in no gods, and may have never heard of "weak athiests" or soft ones.
I call myself soft because I'm not interested. Pass the ice cream.
On discussions on christian threads, I don't think I've ever posted on one. I don't mind they exist, I just don't participate.
I do participate in the few threads we've ever had for atheists to talk with each other, softly or loudly or snoring.
edit to add - I think some fair amount of people who state "no religion" are not using the word atheist because of a sense of spirituality re the world. I've an atheist friend who thinks mountains are spiritual places. I like them as mountains. Not very different, really, but still a difference. Others may consider spiritual quite seriously, avoiding the word atheist.
To each his own.