I've always had a problem with this concept.

A normal stomach is highly acidic. It would denature most
enzymes as described on that site. Enzymes occur in all living things. Mostly they are involved with oxidation of compounds into energy, for the cells. They are peptides, which are acid unstable for the most part. Here is an example of one metabolic path in humans:
http://www.genome.jp/kegg-bin/show_pathway?map00471
This is the conversion of glutamine to glutamate. Every box with a number is an enzyme involved in adding or removing a portion of the substrate during conversion.
Most of the enzymes in the body do things like this. They do not digest food. Most of the enzymes in the food we eat also exist for many purposes other than digestion.

Digestive enzymes do not get added to food until the stomach dumps its contents in the beginning of the small intestine. There the pancreas serves up high bicarbonate to neutralize the acid
and also adds the digestive enzymes at that point.

However, modern man now tampers with the stomach and millions of people have no acid to speak of.

This theory therefore confuses me. There are people who cannot digest raw food well. And there have been legal cases of children taken away from parents who fed them raw only and those children died (failure to thrive). There was just a huge trial from Florida about this involving a husband and wife.
Raw food also carries potential serious pathogens. Cooking food evolved to make it safer to consume.

Here is a more thorough discussion of the pros and cons of raw food movement:
http://en.wikipedia.org/wiki/Raw_foodism