The bubble-tip anemone, Entacmaea quadricolor, has spawned at the Waikiki Aquarium. I've never heard of it happening in home aquaria though. Some important things to remember though if you did try to get them to spawn is that they will need pristine water quality, and that the spawning event(s) will very quickly degrade that water quality. Even at the Waikiki Aquarium the spawning so heavily degraded the water quality (by reducing oxygen levels) that many clownfish were left gasping or laying on the bottom, and a bicolor angel died as a result. Even they had to perform a 50% water change, add airstones, and increase flow in the tank. Granted, this was a 350 gallon tank with several dozen anemones spawning, but you get the idea. I suspect tank filtration and skimming would also kill a great many of the fertilized eggs. This is a fairly slow growing species as well, so should you be successful it would take quite a while before you really knew what you had. All that being said, I would not in any way discourage you from trying. The worst that happens is they don't spawn and only split, giving you a nice tank full of anemones to trade or sell. If they do spawn, great! Keep us informed if you do decide to go ahead and try a breeding program.