You may have noticed the hullabaloo last week over the news that Yahoo!, a weighty Internet giant, had paid $1.1 billion to acquire Tumblr, a blogging platform allegedly popular with the yoof of today.

What you may not have noticed is the declaration by Marissa Mayer, Yahoo's reformist CEO, about her latest trophy acquisition. "We promise not to screw it up," she wrote on the company blog. "Tumblr is incredibly special and has a great thing going. We will operate Tumblr independently. David Karp will remain CEO. The product roadmap, their team, their wit and irreverence will all remain the same, as will their mission to empower creators to make their best work and get it in front of the audience they deserve. Yahoo! will help Tumblr get even better, faster."

As mergers and acquisitions go, this is surely a first. Usually what we get after the consummation of these dangerous liaisons is corporate guff about "synergy" and "efficiency gains." Yet here we have a CEO declaring that the one thing she will not do is destroy the outfit for which she has just paid a shedload of money. (An outfit, by the way, that had just $14 million in revenues last year.)