It's hard to believe that Stumble Upon one of the first real social bookmarking sites is still so popular. But statistics show that with a Facebook almost 400X that of Facebook and Twitter, Stubmle Upon is here to stay! Most people thought that Facebook links have longevity, they don't - they have a few hours of virility but little in terms of life. Where as Stumble actually has a longevity of not just hours but days and weeks (months in some cases). From this study it looks like maybe we should all be using Stumble Upon a little more!