It's not a good idea.

I was leaning forward with my hands on the back of one of those chairs after the tunnel forum last night, chatting with some city hall staffers, and the back of the chair popped right off (well looky there, it just pops right off!) and I did a face plant on the ground, at the feet of said city hall staffers. Gotta hand it to them, their manners were impeccable: They were smiling hard, but none of them outright laughed, even though watching someone fall on their face is literally the funniest thing in the world.

(The lady on the treadmill at 3:35 for the win!)