Now that Yahoo has officially unveiled its plans to purchase Tumblr for $1.1 billion, it's inevitable we'll see some user backlash. Rival blog host WordPress claims that backlash has already begun: founder Matt Mullenweg says that imports from Tumblr to WordPress rose from the typical rate of 400-600 per hour to over 72,000. That's quite an uptick, although it's worth pointing out that the number cited relates to individual posts, rather than entire blogs. It's also not unprecedented: as AllThingsD notes, Posterous users fled the service when it was purchased by Twitter, and Instagram users were up in arms over its acquisition by Facebook.

Mullenweg also made some comments on the acquisition as a whole. He believes that the price Yahoo paid for the blogging platform may be seen as a steal in the future. Although he calls the all-cash price "very generous" by some metrics, he believes "it’s a tenth of the value that will be created in these platforms over the coming years." Mullenweg added that he's "curious to see what the creative folks behind Tumblr do with their new resources," but lamented that we won't know what they would've done if they continued to run Tumblr as a private company.

Update: Mullenweg now says he doesn't "think there will be any sort of exodus from Tumblr." He believes, "for most folks," habitual behavior overcomes "internet outrage." He also notes that, "even if a million people left," it wouldn't have much of an impact on Tumblr's massive user count.