This was an excellent post. I have actually thought a lot about this myself. A lot of my concerns are health based its actually somewhat difficult to replace complete proteins in a pure vegan diet. Also, having a lack of meat or fish in a vegetarian diet can make it hard to get enough Omega 3 and Vitamin D in their diets.
Environmentally, vegetarianism can cause significant ecological harm. Many farms and produce producers unless they are truly 100% organic usually use pesticides and insecticides that kill plenty of other animals like insects as well slowly damaging the water supply for people.
Yeap, many health implications are involved. Many vegetarians comfortably avoid them.
Yeap, pointed that out in the article. In Australia this is a massive problem.