StumbleUpon announced that it has reached a new milestone . It has acquired its 10 millionth user. The company broke away from eBay a little over a year ago. After that, it released its "web bar" feature as well as a new version of its Firefox add-on, a Chrome extension (which last month StumbleUpon claimed was one of the top 20 third-party extensions), and its content syndication service Su.pr . They also released a revamped ads system,