I am convinced that stupid people routinely apply to be on this show. Those that are convinced that plying their guests with alcohol with lead to higher marks, those who deliberately attempt to score low (inevitably, as another reviewer said, this tends to be the women), and those who are convinced that they are the greatest thing ever and come across as the most vile and reprehensible creatures known to man.
With that being said, I absolutely love this show. The narration is hilarious, the banter between contestants and occasionally a good fight make it compulsive viewing. I really couldn't care about the food - it's the interaction that's so good to watch.
The only exception is the celebrity editions: these tend to be filled by Z-list personalities, intent on talking over each other and (apparently) not even filming in their own houses on occasion. For that reason, I give Come Dine a 9.