Google's Personalised Search
Search on the internet is changing. We all know how Google works - you type in your search term, hit the "search button", Google beavers away in the background trying to match what you typed with the most likely matches and you're presented with a list of results, all within a split second.
If you are logged into Google when you do the same search things are now slightly different. Once the results come back you are given further options. You can "promote" a site by clicking on the little up arrow next to it. This is your way of saying that this is the site you wanted and it will push it to the top of the list for next time you do that search. You also have the option of clicking "remove", the cross. This means that the result is not relevant to you and won't be shown next time around. Finally, you can "comment" by clicking on the speech bubble. This allows you to make notes as you go.
It doesn't stop there though. Google doesn't just remember your feedback on searches you have done but uses this information to predict your areas of interest. For example, if I do a search for "ajax" it will, in all probability, return results on Ajax the web programming technology. For someone else with no interest in web development but an interest in football it may return results on the Dutch football team.
The wider effect of this new personalised search is that as people start making use of it then what one person sees when they perform a search may not be what another person sees. In fact, after prolonged use it almost definitely won't be. This means that the SEO companies who claim that they will get you top rankings on Google will no longer be able to measure how well your site is faring. They will be forced to revert to using numbers of visitors to a website as a measure of success instead, which, as any marketing person will tell you, is the only real measure anyway.