The correct verdict was made. There was not evidence enough to prove beyond a reasonable doubt that Casey Anthony murdered her daughter, and in the US criminal justice system, you are SUPPOSED to be innocent until proven guilty. Guilt of murder was NOT proven.
Casey anthony's life is ruined. She's not "walking free." She has spent three years incarcerated, and those three years of incarceration occurred without her having been convicted of a crime- BUT she WAS incarcerated as a woman charged with killing her young daughter, which must have added an extra level of hell to the experience.
What should Casey Anthony HAVE been found guilty of? The neglect charges which were dropped when she was charged with murder. Even if her story is true, she should have prevented her daughter from having access to a pool in which she could drown. Based on what we know of her, her behavior, and her character, it's also extremely likely that Casey was a bad enough parent that she could accurately have been labeled as "abusing" her daughter, over and above simple neglect. But, even the "aggravated abuse" charge that DID remain, there was not sufficient evidence to support. Casey wasn't a good mother. She is probably a terrible person. Unfortunately, "being a terrible person" isn't something she could be charged with.
No judgement passed on Casey will bring her daughter back. No verdict will keep her from being one of the most hated women in America right now, nor from having this be something that stays with her forever. There was no chance at "justice" in any of this, guilty, or not guilty- it's a horrible tragedy that was turned into a media circius.