An anonymous reader sends along this excerpt from MIT's Technology Review:
"Personalization is a key part of Internet search, providing more relevant results and gaining loyal customers in the process. But new research highlights the privacy risks that this kind of personalization can bring. A team of European researchers, working with a researcher from the University of California, Irvine, found that they were able to hijack Google's personalized search suggestions to reconstruct users' Web search histories (PDF). Google has plugged most of the holes identified in the research, but the researchers say that other personalized services are likely to have similar vulnerabilities."