An uninformed strict vegetarian is at special risk for what deficiency?

Protein, Vitamin B12, iron and calcium.

Hmm, B12 I'd agree with for a sloppy vegan diet only. B12 is made by microorganisms inside living things and so is found in animal products and meat. Vegans are more at risk than vegetarians because vegetarians can get it through dairy and eggs.

However vegetarian foods, flour and margerines are often fortified with B12 and Iron. Also seaweed and yeast extract are vegetable sources.

The other stuff is quite abundant in vegetables, you'd be surprised at a lot of sources of protein.