I doubt that the enzymes in raw plants are a problem.  A number of raw-foodists I know are people who have some sort of serious carb-intolerance and  ultimately have to go for a 100 percent raw animal foods diet, instead of raw vegan or raw omnivore diets, so that is one possibility. But the real problem with raw vegan diets is that plant foods are not complete foods so there are always some missing nutrients in a 100 percent raw vegan diet, which means people on a 100 percent raw vegan diet will inevitably get nutritional deficiencies over a period of time. Indeed, there has been a  recent development where many former raw vegan gurus admitted that they were eventually forced to eat some raw animal foods as well:-

http://fresh-network.typepad.com/fresh_network_blog/2010/01/the-rise-of-raw-but-not-vegan.html


So, someone who is mostly raw vegan but eats some raw animal foods as well would be fine on such a diet(though I suspect that, for the best health, one would need a higher intake of raw animal foods.

Geoff