Even before the acquisition was officially announced this morning, on onslaught of users importing Tumblr blogs to WordPress already began. That is, at least, according to WordPress Founder Matt Mullenweg.

He writes, “Imports have actually spiked on the rumors even though it’s Sunday: normally we import 400-600 posts an hour from Tumblr, last hour it was over 72,000.”

Despite what would appear to be a mass exodus of users leaving Tumblr for WordPress, Mullenweg appears to think that’s not the case. After he initially wrote the post, he updated it to say, “Some people are reading too much into the import numbers — I don’t think there will be an exodus from Tumblr.”

He then pointed readers to the comments on this post, where he said, “I don’t think there will be any sort of exodus from Tumblr. For most folks habits overcome internet-outrage. Even if a million people left, that’s just about a week’s worth of signups.”

Even still, other blogging platforms are likely to get a little bump out of this.

According to a recent report from Pingdom, WordPress’ share of the world’s top blogs has already been on the rise.

If you are unfamiliar with Tumblr, know this: there is a lot of porn on Tumblr – artsy nude content, straight up porn, pretty much all colors of the NSFW rainbow. It makes up a significant part of the Tumblr landscape, and without it, Tumblr wouldn’t really be Tumblr. Some Tumblr users are concerned that Yahoo will waltz in and attempt to change all of that. Before the acquisition went official, some analysts worried that Tumblr’s NSFW underbelly would be an issue for the folks at Yahoo who were considering the deal.

But it wasn’t. Now that the acquisition is official, it’s looking like Yahoo is committed to keeping Tumblr running as is, and that the porn problem, well, isn’t really a problem. During her conference call to discuss the deal, Mayer had this to say when asked about all of the “not-brand-safe” content out there on Tumblr.

“The width and breadth of content on Tumblr is what’s exciting and has allowed it to reach more users.”

And when it comes to possible concerns from advertisers? Well, Mayer noted that Yahoo will just have to have good targeting. Mayer said that Yahoo is going to put more ads inside the Tumblr feed, so we know it’s coming. But Yahoo can pick and choose where they throw those ads, and can steer clear of any content that may concern potential clients.

“We promise not to screw it up. 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,” said Mayer in her announcement.

And in his, Tumblr CEO David Karp said that “before touching on how awesome this is, let me try to allay any concerns: We’re not turning purple. Our headquarters isn’t moving. Our team isn’t changing. Our roadmap isn’t changing. And our mission – to empower creators to make their best work and get it in front of the audience they deserve – certainly isn’t changing.”

That sounds like Yahoo is going to adopt a fairly hands-off approach to the Tumblr, and that’s good news for Tumblr users. Sure, people lie and things change, but as of right now it appears that Yahoo isn’t that concerned about all of those naughty parts on Tumblr. Carry on.

According to the firm, 52% of these blogs are using WordPress, up from 48% a year ago.

To come up with the top blogs, Pingdom looked to Technorati, which is famous for its annual State of the Blogosphere report, which has transformed into the “Digital Influence Report“. It’s worth noting that Pingdom was only able to identify the platform in use by 94 out of 100 sites.

As you can see, the next largest piece of the pie comes from custom systems, followed by Drupal, N/A, Gawker, BlogSmith, Movable Type, TypePad, Blogger, Ceros, Joomla, and Tumblr.

Considering Tumblr’s rising popularity in recent months, it’s interesting to see it carry such a small percentage here (1 site).

TypePad has increased from two sites to four sites, while Movable Type decreased from seven to four. Drupal dropped by one site. Google’s Blogger gained one site, reaching three.

Here’s the list of blogs, and which platform each uses: