Subscriber (user) retain ownership to his/her content, so ownership is not transferred to the service owner.
Subscribers preserves a reasonal privacy, even though user name and email address are shared by default. The user is able to change visibility of the email address and take his/her own blog from public lists.
Changes in Terms of Service are posted in the service and possibly with email.
The service is based on public sharing of content, which emphasises the need of consideration when sharing content. This is also expressed in Terms of the Service.
Tumblr reserves the right to reshare public content uploaded to the service and to perform analytics with third parties.
A Tumblr account must be created. Anonymous browsing of content is however possible.
A link to support request form is on the main page of the service.