I think, with syllubi the way they are now, plagarism is almost becoming unavoidable. Every dot point has been summarised by hundreds or thousands of people, there is nothing new to say and the best way of expressing something has already been done. I think the incentive is definitely there to plagarise. I do Philosophy, no one would be stupid enough to plagarise in that (the entire candidature for the course only totals 56 and everyone including the markers have access to the past students' work on the Philosophy website, etc). I also do Chemistry and Physics, and I would think that plagarism in assignments in those subjects is probably the most common of all my subjects (in addition to the above 3, 4 unit maths and adv. english as well as Geog which I accelerated). The wide range of material posted by past students on a site like this must be simply too tempting for some students. Most people pre-write english essays but I don't think plagarism is all that common because there isn't really that much information around on what people write their essays on (eg: "compare the techniques used to convey the similarities and differences between Emma and Clueless" or "refer to the stimulus booklet...", good luck finding something useful to do with that on the net).
I have plagarised a number of times before, but never for an HSC assessment. It's just too risky. The past instances have been in stuff like RE assignments and other meaninless things like that.
Plagarism isn't just copying word-for-word, the half-arsed approach is definitely to just change a few words and perhaps the order of them a bit. It's still plagarism.
In the end, the student loses out because if they are lazy enough to plagarise, they are bound to be too lazy to actually learn what the didn't learn as a result of the plagarism and hence will be screwed come HSC time. People will tell themselves "it's ok I will learn it later" but I bet they never bother and conveniently forget.
