We really need a ratings system.
When I'm on the bus, and there aren't any open seats (meaning, I'd have to squeeze in next to someone), I elect to stand.
If we're honest with ourselves, we know that no one wants someone to sit next to them. They want to sit alone. So I accommodate this and stand.
To me, standing vs sitting next to someone are about the same. I'd provably a little bit rather sit, but knowing they don't want me there, I elect to stand.
The exception to this is if the bus is super crowded. In this case they're gonna end up with someone sitting next to them anyways, and it's also way less comfortable to stand as a sardine, and so the scales tip where sitting is better.
So I have to admit, I feel robbed when someone sits next to me in a spot where I wouldn't do the same to them.
"well.. well, some people aren't as physically fit, y'know.. it's not easy for everyone to stand"
Which is exactly why they have he reserved seats up front for the elderly and in need. If you can balk at those and walk to the back of the bus, then you can stand.
With a robust p2p ratings system, I could go down as one of the people who stands, and get some kind of value out of it. (Perhaps it would be in the form of an implied reciprocity to not sit next to me, and a demerit if you do).