It's interesting juxtaposing this conversation with the book I'm currently reading, the Power of Play by David Elkind. He discusses how play, love and work complement, not oppose, each other during each major phase of children's growth.
He asserts that when play, love, and work are all involved, learning and development are most effective. Based on that, I would say hothousing would be work divorced from play and love.
Elkind described a mother showing her 8-month old flash cards with pictures of presidents on them because "if you stick with it, they will come through for you." He describes this failure to take the needs, interests and abilities of the learner into account and this also sounded like a good description of hothousing.
Reading it has confirmed much of my judgment about what crosses the line between finding a child's zone of proximal development (or the "sweet spot" as Kriston put it so well) to hothousing.
