That's true - my friend has an arthritic condition that's not evident but sometimes needs a seat. That's why I will never ask for a seat unless I really feel I need it -asking is actually really difficult and uncomfortable for that reason. And that experience has definitely put me off, which is why I decided to find an alternative route to work. For what it's worth I don't think he needed the seat, and if he did he could definitely have reacted in a more reasonable way as I don't think it's unreasonable to ask if you are obviously pregnant (with a badge!) and struggling in the heat. If someone said politely that they needed it too I certainly wouldn't question them about why and I don't think many people would. It's an eye opener - I suppose if you are the sort of person that always offers you naturally expect that other people will - they rarely do. I find that teenagers and young people are wonderful, strangely it's the businessmen in suits that pretend they haven't seen you!