By The Staff July 12, 2012 11:59 am July 12, 2012 11:59 am In this week’s magazine, Rob Walker profiles David Karp, the 26-year-old founder of Tumblr, the blogging tool and social network. Tumblr has been used to make more than 60 million blogs, and we asked Karp for a few suggestions — and examples — of what qualities make a good Tumblr stand out. Here are three of his suggestions: Be inventive.