An anonymous reader writes "By creating a distinctive username—and reusing it on multiple websites—you may be giving online marketers and scammers a simple way to track you. Four researchers from the French National Institute of Computer Science (INRIA) studied over 10 million usernames—collected from public Google profiles, eBay accounts, and several other sources. They found that about half of the usernames used on one site could be linked to another online profile, potentially allowing marketers and scammers to build a more complex picture the users.
"These results show that some users can be profiled just from their usernames," says Claude Castelluccia, research director of the security and privacy research group at INRIA, and one of the authors of a paper on the work. "More specifically, a profiler could use usernames to identify all the site [profiles] that belong to the same user, and then use all the information contained in these sites to profile the victim." ...."Link to Original Source