Actually, there have been quite a lot of inadvertant releases of buckets and so it is a real risk. Also, there's a bit more of a temptation to pull water from backyard pools with a bucket (I know, the tanks can also but they tend not to be as 'long'). The work that HA has done with the B3s in Perth I understand has been very successful. It works in that environment - it may not be the best in other environments....horse for courses so they say.