I bought a Bumbo when Isabel and Adam were infants. I thought it was one of the greatest inventions ever - it allows small babies to sit up before they can sit unassisted. The label on the Bumbo package clearly states that you shouldn't set it up on a countertop or table.
Then I found an even better picture. Isabel in the Bumbo on the kitchen counter. Even better, the other two kids are sitting next to her on the counter, unsecured. I assure you it was just to snap a picture and I was ready to catch all of them at once at any moment.
Lessons learned: Still use the Bumbo with the next baby, although not on top of things. Do not, under any circumstances, put a bouncy chair in an unstable, high location. And if you put all of the kids on the counter for a picture, have another adult nearby for safety reasons.