Roundtop was still doing it 2 years ago - last time I skied it before moving to Philly area! I loved the small bumps they had on a blue run at Roundtop! I haven't skied Camelaback so can't speak about them. Montage has some great bump runs. Jack Frost occasionally has seeded bumps on the sides of their wide groomed runs and so does Blue Mountain.
I will add my prospective I am still earning to ski bumps - I am comfortable/enjoy small to medium bumps and easy trees, but still scared on really big tightly spaced bumps. Yes, absolutely there are some technique basics like the instructors in this thread already mentioned - pivoting, fore/aft balance etc that need to be honed/developed before attempting bumps. And fully agree that bump lessons are the best way to go.
But also what I have discovered - there comes a point in ones skiing, at least I came to this point. I have most of these trachnique basics down and plenty of practice in many lessons on groomers, now I just need to practice it in bumps and ski bumps. I have had several instructor comment in lessons that I have such good technique and that it's strange that I still can't comfortably ski all kinds of bumps. I am definitely capable of executing round short radius turns with pole plants on groomers, can't always do it bumps. Sometimes I just can't make myself turn, once I start turning and pole planting things usually go well. It's almost like this strange mental coordination issue I have to overcome. There is a fear element too, so maybe it's a mix of fear and coordination issue. I am getting better overcoming it slowly, so mileage with more lessons is my current priority for improving my skiing bumps right now. I have skied some medium difficulty bumps this winter and felt like I was flowing them and having a great time. But then there were times I skied similar difficulty bumps and was making 2-3 turns and stop.
I would actually say I only partially agree with the expression that "it's not that you can't ski bumps it's that you can't ski and bumps show it". This expression doesn't take into account mileage/fear issues for the skier, just that there is a lack of technique issue. Great ski technique is not enough to ski bumps well, it's the very first necessary step in learning to ski bumps IMHO. The other steps are mileage, coordination, confidence, line choice which comes with mileage - those are unique to every skier. At least that's how I think about it. I'm not an instructor though, just someone who has taken many lessons.