I've seen some speculation (based on anecdotes) that juries now frequently exhibit what's called "The CSI effect." They want absolute proof of guilt, so the theory goes, because the various iterations of CSI ("CSI Traverse City," "CSI Edina") have conditioned them of the need for massive sciedntific evidence in every case, particularly the high profile ones. And they have become less amenable to circumstantial evidence.
The two big escape hatches in this case were the suggestions that Casey Anthony had been sexually abused and that the baby died as a result of an accident. There was no direct evidence presented that either circumstance prevailed (the judge precluded her lawyer from discussing the sexual abuse because there was no evidence). Despite those facts, did the fairytales about abuse and an accident impact the jury? Does the mere mention of an "explantation" absent any evidence constitute "reasonable doubt?" Is that "reasonable?"