Maybe this a bit of geographic/demographic issue - I know in my neighbourhood the AP families are easy to spot - the carry their babies, breastfeed and both mums and kids radiate a really positive energy. I practically soar when I see a family and we exchange looks that lets us know we're in the same club, on the same team. It's been pretty snowy here lately, but a few weeks ago, my dh and I were walking to the grocery store, pulling our cart, carrying dd in her backpack, and we came across a family that was just coming back from the grocery store - daddy was pulling two toddlers plus groceries in a wagon, through the snow, and mummy had a new baby in a Snugli with her jacket zipper up over the babe. We looked at each other, and just knew. When we see each other in the park, when it gets nicer out, for sure we'll get to know each other better. I just don't get that feeling from the other families, screaming at their kids, carting around babies in all manner of buckets, shoving binkies in to keep them quiet, grocery carts filled with red dye number seven crapola and bottles of pop - the grocery store is a very telling place.
And Moon, I know it's true that SOME formula feeders have legitimate reasons for doing so (adoption, surgery, chemotherapy, etc.), but the vast, vast majority do not. I have a girlfriend from Rwanda, and she has never even heard of a woman who couldn't breastfeed. I think it's very interesting that in countries where women have no access to formula, 99.99% of them can miraculously breastfeed. You shouldn't be made to feel like a scumbag, but I think you need to understand that very few formula feeders are dedicated AP mamas who WOULD breastfeed if they COULD. I would definitely think twice before approaching any mother I saw with a bottle of formula. It's true that there is a slight chance that I am misjudging someone, but there's an even greater chance that I simply do not share similar parenting philosophies, and in my experience, I need to be on the same page with my friends in terms of parenting styles or it just doesn't work out.
It's easy to say "never judge" in theory, but in practice, we are all making judgement calls every moment of our lives. That's just reality, I think.