On a chilly Tuesday morning from Boston, Aaron in for Adam today.

It was tweeted repeatedly yesterday, after news broke that David Karp, the founder of Tumblr, was leaving the free-wheeling blogging site that’s now owned by Verizon via its recent acquisition of Yahoo. “Tech history: Facebook’s Mark Zuckerberg acquired Instagram for $1 billion in 2012. Yahoo’s Marissa Mayer bought Tumblr for $1.1 billion in 2013,” noted CNBC’s Tae Kim, in one typical tweet.

Tech history won’t have many good things to say about the Tumblr acquisition. The site’s anything-goes ethos, with a heavy serving of porn, was always an odd fit with Yahoo’s more mature audience and advertising base. Though Karp stayed, he and his new Yahoo overseers never found a way to sell much advertising on the platform or keep it growing at a rapid pace. And they fumbled the transition to mobile. Before disappearing into Verizon (VZ) and its new Oath media unit, Yahoo had written off the value of two-thirds of the purchase price.

The story of Instagram at Facebook (FB) is almost the exact opposite. Mark Zuckerberg didn’t just keep CEO Kevin Systrom, but also allowed Systrom to direct the platform’s future. Instagram stayed focused on mobile users and turned into a perfect platform to host sponsored posts. In weighing the best acquisitions of all time, the investing-oriented web site Benzinga placed Instagram second behind only Google’s (GOOGL) $1.65 billion purchase of YouTube in 2006.

Karp gave no hints about possible future projects on his way out. “I beg you to understand that my decision comes after months of reflection on my personal ambitions, and at no cost to my hopefulness for Tumblr’s future or the impact I know it can have,” Karp wrote in a letter to his employees that he also posted on his Tumblr blog. “The internet is at a crossroads of which this team can play a fundamental role in shaping.”

The more interesting story to follow won’t be what happens to Tumblr, though. It will be how Karp next tries to shape the the future.

(Full disclosure: I worked for a few years at Yahoo Finance, but had little or nothing to do with Tumblr.)