What do you think when I say "scientist"?

I was crawling through one of my favorite sites at the moment, io9, and came across a recent story about a man recently cleared of a number of charges stemming from his possession of bacterial cultures in his home. Where did this "mad science" stigma come from, I wonder? Has the hollywood portrayal of the evil genius cooking up destruction in his private liar/lab become so ingrained into the public's mind? I'm a scientist. When someone asks me what I do I'm proud to tell them that I'm a microbiologist. But I have, on occasion, wondered what what impression that makes on the person I'm meeting. Do they imagine that I'm concocting potions with wild abandon? Running around my lab with wild hair in my stained lab coat, muttering to myself?

I'll admit to the bit about the hair and lab coat, even to muttering on occasion. But for the record, I suck at potions.