FSP has a recent post about being attacked when/after giving a presentation. The post has a poll which shows that the majority of respondents have indeed experienced a public rude comment/question during or after a talk. A rude question would be one that attacks the speaker and his/her research personally or is clearly intended as a "gotcha" question.
I think geologists are pretty laid-back in general. In my experience, folks tend to ask more pointed/technical questions of a speaker who seems to know what they're talking about. Undergrads and the clearly nervous tend to get a pass. However, the questions can get more pointed if someone is
representing a company (say, a remediation firm) and the presentation
sounds more like a sales pitch. For example, they have some new
wonder-formulation that will work in all types of geology and has no
field implementation issues at all.
I did have one person who had published several papers in my corner of the environmental field and seemed to take my research personally, and he was pretty aggressive when I was giving talks. He didn't like my scope of research and timeframe, and he would point this out every chance he got. I responded that financial and time constraints (there's only so much a master's student can do with a fieldwork-based project!) prevented me from designing a gold-plated research study, but that initial results were promising. And yes, I was aware of his work. And I was not actually doing what he did, I was looking at his subject from a different angle, using distinctly different methods.
After the second go-round, I was rather practiced at this.
I don't think I've actually been at a presentation where someone was attacked personally or told that their science was a waste of money. I'd like to think that if that were to happen, the audience would give a collective shrug and ignore the question to discuss the actual science.