Time and time again, taking supplements are shown not to convey the same benefits as a healthy diet does. And, also as in many other previous cases, supplements are shown to have measurable risks. Past examples include Vitamin E, Vitamin C, and beta-carotene.
Since you are a vegetarian, you would probably find "The Food Revolution" by Jonathan Robbins a good read. It has a lot of statistics on bone health, Ca intake, vegetarians, meat, and milk.
add: I am curious what you mean by "hard to get enough calcium." How much are you presently getting by diet alone?
Everywhere I look, I see a Ca requirement being 1000 mg (I'm in the US). Animal protein, colas, smoking, being sedentary, and some other things have been shown to increase your excretion of Ca, so people that that applies to might be wise to consume at least the RDA.
Robbins makes some pretty good points that the Ca requirement could be much lower for an active vegetarian or vegan.
My understanding of that study was that it was the sudden influx of extra calcium and only occurred in people that were older. but, I haven't read the study in like a year. Sorry if that's not helpful.
What you eat can have a direct effect on your skin if you're struggling with psoriasis. See what to shop for.