Tumblr has made and official statement on twitter about what’s going on:
We’re committed to helping build a safe online environment for all users, and we have a zero tolerance policy when it comes to media featuring child sexual exploitation and abuse. As this is an industry-wide problem, we work collaboratively with our industry peers and partners like NCMEC to actively monitor content uploaded to the platform. Every image uploaded to Tumblr is scanned against an industry database of known child sexual abuse material, and images that are detected never reach the platform. A routine audit discovered content on our platform that had not yet been included in the industry database. We immediately removed this content. Content safeguards are a challenging aspect of operating scaled platforms. We’re continuously assessing further steps we can take to improve and there is no higher priority for our team.
Please please please, for the love of everything, stop spreading fear in our community. They are not purging your blogs for having NSFW content. If your blog gets deleted and you didn’t have any of the above mentioned content, or something that could be percived as such, then please contact Tumblr Support to regain your blog. They can be contacted via the form here.
Please reblog so people stop spreading false information and cause unnecesary fear.