YABU, When did we all become so intolerant of others 
Yes people should be more considerate of other bus users, but that's all people, not just those with buggies.
I agree that if you are a regular bus user (everyday in my case) you should have a suitable buggy. I've got a baby jogger which isn't massive and without doubt is the easiest to fold, I got it because I wanted a bus friendly buggy, but it's still a massive PITA to fold the buggy and hold on to a toddler+his nursery bag+my bag then hold his hand onto the bus, show my bus pass and carry the buggy+bags, then find a seat for him, put him in it and hope he stays there/holds on/doesn't go flying at any point because the luggage space isn't suitable for a folded buggy, it's a shelf so the buggy's unsecure and will fly off everytime the bus goes round the corner if you're not standing holding on to it, so you have to stand in front of it, causing more of an obstruction that the unfolded buggy.
Thankfully when I had a bugaboo (given to us, couldn't afford to buy anything) and I had to fold my buggy, 9/10 times other passengers or the driver have helped and held DS's hand while I folded it/held on to it while I sat with/carried DS, but you can't always guarentee helpful people being around.
And not everyone gets to choose their buggy - a lot of people are given them and can't afford to buy a light/small/easliy foldable replacement, and they have to be able to lay flat until at least 6 months so no, not all umbrella folds are suitable from birth, and not everyone can afford one buggy for 0-6months and another for 6 months plus
Really, buses should be better designed.
And that should be the focus not telling parents to buy a new buggy and/or fold it every time just in case it MAY inconveince someone else for 3 seconds by mildly knocking a knee/elbow BY ACCIDENT. I highly doubt they're knocking people on purpose
Buses here actually aren't too bad, they can easily fit a bugaboo along the aisles without upsetting anyone, have seats that keep other passengers legs/feet out of the aisle and room for 3/4 buggies or 1 wheelchair 2 buggies. But it's still a faff having to fold and carry.
The best ones IMO are in Brighton, they have a dedicated wheelchair space on one side that can fit 2 wheelchairs AND space on the opposite side for up to 5 buggies depending on their size/which way they're parked - I've never been asked to fold on one because I've never needed to.
Most bus companies regularly replace their stock regularly anyway, so why not get better user-friendlier ones when they do?
mrsgruffalo and all the others who agree can I ask a)if you use the bus regularly b)if you took your DC's on the bus and folded your buggy without fail and c) if you have ever had to manouver a small baby+bags+buggy and how do you suggest buggy users get round this, because it's all coming accross a bit judgeypants at the moment
And I was under the impression that small easily foldable buggies are a relatively recent thing - my Mum and all her peers all had enourmous silver cross types in the 70's, and she's said a few times that when umbrella folds came out in the 80's they were a godsend (10 year gap between me and older sibling)