Yeah, I have found some people to be downright rude when they follow up the "no, not yet" with a question like "Oh, youre having too much fun making money still?" or some other rubbish. My exboss asked me I dont know how many times "so when do you think you will be ready to have kids?" and our neighbour even said "how old is she?" to DH followed by "well you better not leave it too much longer then". I couldnt believe it when he told me, I just wanted to go next door and punch her!
I agree with Bath that people do ask things now that they would never have dared to ask a generation or 2 ago.
Generally people understand when you give them a short, polite answer but some people who ask more bold questions might need a bit of a bolder answer. I got caught in a trap one day by someone I dont know very well who asked all kind of questions and I felt myself answering them and inside I was like "what the hell am I telling her this stuff for?". I really wish I had said that it was just something that I didnt want to discuss and leave it at that.