Did you know that you can easily see how a certain website looked like let's say 5 years ago? Internet Archive: Wayback Machine (www.archive.org) allows you to type in a url and go back in history. It is a fascinating tool that can be extremely useful for SEO purposes. Link builders can use the Internet Wayback Machine to effectively utilize abandoned domains. If you get a hold of an abandoned domain name that has lots of backlinks pointing to it, you can look up what was the main topic of the abandoned site (using the Wayback Machine) and then recreate the content of the new site. Once the new site has been setup with the proper (or new) url structure, you can then follow up with all folks who linked to the abandoned site and ask them to consider changing their links or include more links to the newly updated content.
To give you an example, see how Google.com looked like back in 1998 when it started (http://web.archive.org/web/19981111183552/http://google.stanford.edu/):