[DerpObvious]

> In practical terms this means that any individual or business hosting having a Facebook profile page or blog on Tumblr could be sued.

This just says that they're responsible for the effects of the services they contract, in addition to acts they undertake directly.

Should a person building a bridge get out of the liability because they contracted out parts of the work? No.

Neither should the operator of a website because they opted to use services provided from a third party for part (or all) of their web services.