I'm busy designing a web site at the moment,which essentialy is science & technology based. I need a specific type of image to 'pad' out the site so did a search Google images. Hey presto.......hundreds. Then I thought about copyright issues, so have sent a barrage template of emails to the web site owners asking to reproduce their images. Most have said 'yes..not a problem', three flat refusals and some unanswered. So I took it one step further and googled DMCA, take down notice and plagarism. Some frightening stuff out there. I came across this scary piece of kit http://www.duplichecker.com I did an experiment. Copied strings of text from random web sites and stuck it in duplichecker. I was amazed at how many times chunks of passages were echoed, getting dozens of hits. This went across the board. Personal, business, journals. You name it. The cribbers have been bang at it. I wonder how many folks have been guilty of poaching a little text here and their....not to mention the odd .peg. Any experiences? Do the DMCA run a reward scheme?
To get back to your question, of course there are "incentives" the copyright vampires give to the law firms hunting private citizens down. Actually, even without them, these legal notices with their usual blackmailing attempts ("pay $$$$$$ before ##.##.## or we will start a lawsuit") make these shark firms so much money (with the price of ruining countless existences) that they would do great even without that... :-(