I want to dispel the rumor going around telling you to boycott the terms of service change for Tumblr because they’re taking ownership of your content. I dug around and actually read it.
It has a bit about privacy stating that they can share certain information of yours with other entities (it has a hyperlink to show you which entities and what information but I didn’t check. I’m not the type to worry about this, but I know some of you are). Anyhow, I think this screenshot makes it pretty clear that your stuff will stay yours. Don’t worry!