Read in the newspaper yesterday that google has come up with a new advanced and more accurate search engine. They name it Caffeine Sandbox and the link to it is www2.sandbox.google.com.
It seems that the way they index links and the algorithm for assigning Pagerank and determining your placement on the SERP is new and much more advanced. So i guess all webmasters here getting a steady amount of traffic will have to adjust to a drop as people switch to the new search engine.
In the mean time, lets wait for more news from google on this matter.