Similar to yours, in a way: I taught an introductory PHP class recently (this is me - the guy who thought that PHP was something you did in a dark room with the curtains drawn, and washed your hands afterwards.) I did, however, spend a significant part of the course showing the students how to defang the stuff - and how to test it afterwards, MySQL and PHP ends both, to make sure that it was indeed defanged. I also spent a bunch of time on how to program with "register_globals = Off" and with "open_basedir" set - and emphasizing that they still need to use Suhosin, etc., if they wanted even a slim chance of surviving the Big Bad World of Out There.

As to other 'sins' - well, early on in my career as a consultant, I was quite "hungry" and I'd made some compromises in my work that, on later reflection, I shouldn't have made. Nothing huge or horribly damaging, but they left a really bad taste... and they serve as a very strong reminder not to do that again. Perhaps I'm coming from a privileged position when I say this, but to me, my professional ethics are a stronger motivating force than money. I've turned down several large contracts (2 of them were $10k+ each) because the client and I clashed over what I saw as the ethical implications of doing the work, and he was unwilling to be flexible in that area. I've never regretted those, either.

The pitfalls... oh, this was such a pit that it was funny - even as it was happening. Even though I got fired from that job. :) Right after the break-up of the coin telephone monopoly in New York, I got hired by an enterpreneur type who decided to ride that particular gravy train. He interviewed the hell out of me (electronics, mechanical ability, a bunch of weird tests that turned out to evaluate communication skills, and a polygraph test (!!!)), hired me as a "senior repair technician", sent me to an expensive coin-telephone repair school in Texas, and then... put me in a cage - an enclosure built of heavy wire, a sort of a mini-jail to which I had the key but which was my assigned work area, on the first floor of the warehouse - while all the rest of the techs were on the second floor, in a large open space. More than that, the techs were strongly and explicitly discouraged from "bothering" me in my cage. I repaired all the dead phones that he had during the first two weeks or so - the cage being where they were stored - and went to the Big Boss to ask him what was next... at which point, he vehemently and summarily fired me FOR NOT BEING A GOOD MANAGER. It seems that this was his deepest secret wish for me ("I've treated you as if you were my son, and you've let me down like this!!!") which I had somehow - viciously and intentionally - failed to fulfill despite all the opportunities that he gave me.

I was a bit surprised (although not shocked - I'd smelled something in the wind) at the time, but I give myself great credit for not laughing hysterically right then and there.

I saved it until I'd been out of the building - with my last paycheck in hand - for at least ten seconds. :) I laughed so hard that I dropped to my knees and a cop had to stop by and ask me if I was OK.

-- 
Human history becomes more and more a race between education and catastrophe. -- HG Wells