I think the differences from actual 2- person conversations make people use it differently and make it more bothersome to listeners - including what Janet said. So I think it IS different and causes a form of stress that is real ( meaning stress like noise pollution or light at night) and so I define it as rude when in fact it may not have a precise parallel but is a relatively new phenomenon with unintended consequences for bystanders and we don't have a defined social etiquette for it.

In certain urban neighborhoods one runs across mentally ill people talking to themselves, so that is the first thing that comes to my mind when I see solo folks talking -- not that they are using Bluetooth. Extended convos bother me; short ones not so much.

I think the issue for me is the difference between public and personal space. A phone conversation in a corner where I hear snippets or murmurs is in personal space; a phone call that Is loud enough to be heard several tables away is in public space.

Short, quick calls to check on the kids, or to meet at a pre-ordained spot, are permitted in public space, but extended screaming, abuse, yelling and arguing belong in personal space. The other party can hang up, but the rest of us are stuck with you.

Sensitive, private, or highly personal matters should be discussed in personal, not public, space. Fighting with your partner, firing an employee, discussing your colon issues, or making arrangements to cheat on your spouse are to be discussed only in private space.

Crowded settings where people are packed together and retreat is impossible, are public space. In these public spaces, treating them as your own personal space is inconsiderate--and, yes, rude. If we all decided to do that, life in cities would be unbearable and airline travel unthinkable. If it is truly an emergency, we will bend the rules and do what we can to provide you with more personal space in a public space even if it makes life less comfortable for the rest of us--much like a medical emergency on a crowded plane. It's called goodwill.

Maybe I'm just used to it but it doesn't bother me. Sometimes I find it strange when people talk about really personal stuff in public but unless they are talking loudly in an otherwise very quiet place (like a train or a library) then I don't even notice it.