One example, unfortunately not very scientific: Years ago, I had a bunch of Web comics I visited daily. To make this more efficient, I had a script on one of my servers which scraped the corresponding sites in the morning and produced the daily collection on a single page.

Every few weeks or months, one of the comics would just not appear or not be updated (i.e. there was the same strip day after day). I had to update the code each time, checking the source code and finding the new page and location of the image. Later, some pages started using JavaScript to load the image file, and I lost interest in sophisticating my script. So, no single page comic collection for me anymore. :)