That's correct; Privacy Badger doesn't block anything by default because it doesn't use a blacklist. Instead, it observes the behavior of third-party domains and blocks them based on their behavior. (So it may take a bit of normal browsing before it starts blocking things.)
Also, Privacy Badger recently transitioned from beta to 1.0, so if you last tried it more than a month or so ago, I recommend giving it another shot. And if you find bugs, please report them!
Full disclosure: I work at EFF, which makes Privacy Badger.
I might again, the show stopper bug was me attempting to repeatedly block a domain that would not remain blocked, and it was facebook related so the plugin got uninstalled.