+1 with PeterAit. Why would anyone bother stealing images on with your site, with the likes of Flickr, or a simple search on Google images? Most folks are looking to spruce up their personal pages, desktop, or iPhones. The only way to stop it is to not post the image to begin with.
I've worked in Advertising for over a decade. Anyone worth suing for real money due to copyright infringement already has a legal department and company policies in place to prevent it. Violating such rules will get you fired. Even when our sales-reps or outside employees pull those stunts for their work, we catch it, scold them and buy something from Corbis. It's easier, we find the right image and in the correct resolution that fits the job, (or they had me shoot it).
From a technical standpoint, I still use 250px images due to faster page loads, and can have everything of a given subject in one screen for the over-caffeinated ADHD viewer too see in twenty seconds or less. I only know this because as a buyer I would never put up with slow pages and massive images. Even with today's bandwidth.
You make good points - main one being the people that can be sued for damages are in corporations. These are not the people I worry about.
Damage to reputation comes in many forms - and as another posted, I 've met one other artist who found their images on another website - with another person claiming they were there's.
Anyway its perhaps something we cannot ever control and just like the music business (free downloads and distribution), its a cost of doing business.