It depends on how close you are to that person. Asking someone you just met would be considered rude, but if you know them well enough then it wouldn't hurt to ask. And if they aren't comfortable sharing information like that, then you'd need to respect their decision.
Hmm, maybe. Most people shouldn't be that unwilling to say, though. If some dude came up to me and asked me what my job was and how much I made (we're assuming for this example that I have a job), I'd tell them, but that's just me.
Depends. We newbie graphic designers ask each other and ask around how much people make, especially freelancing just to get an estimate of what's standard and which client is a cheap bastard. Though I would never dare ask someone even from my family how much they make. I don't even know exactly how much my father made a year.
I was surprised that NO only got 14% of the vote, but then again, in this day and age, with everything on the internet for the world to see, and nothing being sacred any more, I retracted my surprise. This might be more of a generational thing, too. I grew up with parents old enough to be my grandparents, and I was always told never, EVER to inquire what someone made, and I never knew anything about my parent's financials either. Now that I'm where I am today, I continue to respect that. It isn't because if I knew they made less than I, I'd want to help out, or if I knew they made more, I'd be envious to the point of hurting the relationship. It's because I don't think it's anyone's business, unless I make it so. And since I don't, no one should be asking me. As it is, the only people who's $$ stuff I am involved with is in my own relationship, unless a friend or family member blabs to me.
It really depends on who's asking and why. I don't think it's necessarily rude just to ask just because some people are uptight about it. Maybe you're just curious about their profession because you're interested in it yourself. In this economy I don't think it's that crazy to ask someone with a job how much it pays.
I do think in certain situations it's rude, but overall I think people are a little too uptight and guarded about this type of thing. I think most of the time people are just trying to get an idea of what your profession pays. Is that so wrong?