Here's a rather interesting tool (http://www.archive.org/web/web.php) that we use frequently at SEP to see how client competitors have evolved and are evolving. To some extent, we can use it to see when a client first tried optimizing their site. Its called the WayBack Machine. Believe it or not, it'll show you a snapshot of what many sites looked like at periodic intervals in the past.
The tool is both interesting and useful from the perspective that it often gives a good indication what a company's product/services were at given points in time, prices for products and services over time, even when a site began its optimisation effort, and if this effort is more content focused or "links" focused.
The tool has records dating back as far as 1996, and you didn't have to submit your site for it to be included in the index.
Check it out when you get a chance ... its quite amuzing. Some of the outdated looks are reminiscent of bell bottoms and mesh shirts, although maybe I'm dating myself. Fortunately, the search engines aren't indexing these relics of the past!