Over on Whatever by John Scalzi is a post on Quentin Rowan's response after being caught plagiarizing the works of multiple authors in order to get published. It's a fascinating example of complete and utter doucebaggery (Quentin's response, not John's post. John's post is pretty much spot on and very fair and balanced.). I recommend reading both.
I've already made a brief entry in the comments section of John's post, but I thought I should elaborate a bit further here on why you will never find me plagiarizing the works of others. There are a few reasons, from least to most important:
1. I could get caught.
I'd have to live in fear of getting caught and exposed to the whole world. My career as an author come to a crashing and unrecoverable halt. At this point, Quentin Rowan's name is mud in the publishing world. He will likely never work in the field ever again. Heck, he was even fired from the bookstore that employed him because of this. No publisher would touch anything he produces now, and even if he uses a pseudonym he's done if anyone ever connects his real name to it, which is much more likely nowadays.
2. I would lose friends.
I've been fortunate enough to make friends within the writing and science fiction\fantasy communities thanks to attending conventions. If I got caught as a plagiarist those friends would disown me so quickly I'd have whiplash. Now, don't get me wrong, these are good people. My crime would be so great they'd have to do it, and rightfully so.
3. I'd always know I cheated.
This is the most important reason for me. Ruin in the publishing world I could live with. Losing friends would hurt, a lot, but I've lost friends in the past through moving and drifting apart so I know it's survivable. Knowing that I got success by stealing and cheating would be what would kill me.
I was raised to take responsibility for my mistakes and give credit where it's due. They are two of the central tenants of my life. Plagiarism breaks both of these.
The comments section of John's original post provides many more reasons that I agree with. In the end, I want to recognized for my work and not something I've stolen. Getting published will be even sweeter when done by my own mental sweat and not thieving from others.