I dont understand how people can genuinely think that her Parents covered her up. It's an interesting theory that adds mystery, but that's all it is IMO.
They would need to plan suitable locations to dispose, CCTV locations, travel etc all in a very short space of time in a foreign location. If indeed they are guilty, why would they need to raise so much money and continuously search after all these years? By carrying on searching and seeking goverment funding, they are allowing themselves to remain in the spotlight, which by now, they could regretfully come to terms with the fact she is gone.
Whilst I do agree that the McCann's are guillty of neglect by leaving their Children on their own whilst they socialise, I think they have been punished enough by having to go bed and wake up each day knowing full well that if they were more responsible, Maddie would not have gone missing. Wandering for their remaining days or until she is found, what has happened and how they could have prevented it.
I also feel awful for the two twins (not sure how old they are now). But I imagine they have to go to School with all the pupils knowing about the documentary that is being aired.