I had never heard of tonka beans before coming across this chocolate, but after a little investigating I can safely say that Thorntons is trying to kill us all. (wayfaringchocolate.com)
I have never heard of tonka beans, but I'm not surprised that it is banned in the US — it wouldn't be the first time random food products are considered poison there, while they are completely acceptable elsewhere. (wayfaringchocolate.com)