This week, I was having a food talk with some of the girls at work and when I said I don't eat something that has butter in it because I'm vegan one of them said "but butter is from nature". Another woman in my work also made that mistake once when she prepared a meal for everyone for her birthday and told me I can eat it because all she brought is organic.
On another occasion, I was at a bungalow for a weekend with a BF and the lady who ran it offered us a breakfast which included omletes and cheeses. When I said I won't have any due to being vegan, she said she has some herbs growing in the garden that leaked there from her neighbors' garden and she has no idea what they are, but I'm sure to know about "these things" and will know how to cook something from them.
One of my professors (!) in my university once mentioned vegans as people who won't take western medicines, but instead take only herbal and homeopathic stuff.
I'm thinking this misconception comes from the fact that in hebrew (I'm from Israel) the word for vegan is derived from the word nature so when people don't know what it means, they make assumptions.
This is a little worrying since, it means people aren't aware of the vegan option to life...hmmm....