I threw this out a couple of days ago, and at the risk of repeating myself, here it comes again:
I still wonder if there's a possibility that Casey was involved in something horrific that did not, initially, involve Caylee. Maybe even involved carrying a body in the trunk of her car. That could explain the cadaver dog hits. In order to secure Casey's silence as to that crime, Caylee was taken. That could explain the continued references to Caylee's safety. And, as has been pointed out, any drug dealer would be hampered by having a 3 year old to take care of. Just speculating on other possibilities. Please don't throw things at me!