HTC Android Smartphone Stores Browsing Screenshots
Mad Hamster writes "Boy Genius Report points out that the HTC Droid Incredible, using the Sense UI, 'will periodically store screenshots of the contents of your web browser.' These shots are stored in such a way that they are not easily deleted. 'They remain when the current browser session is closed, they remain after you clear the browser history, and they remain after a full factory reset,' though there is a way to delete them manually."
The HTC Hero has a bookmark widget that uses screenshots of the websites as the buttons with a small label underneath(which is the websites title text I think). Since these images are called bookmark_thumb, I'm going to propose it has something to do with that...