In "Blog settings -> Features" there is a trackback option to "Allow other bloggers to send trackbacks to this blog, letting you know when they refer to it. This will also let you send trackbacks to other blogs."

I suggest to split this check box into two which control if the blog can (1) send trackbacks; and/or (2) receive trackbacks.

Having both tied together forces decisions on blogger where it should be the blogger who decides. There can be reasons for disabling receiving of TBs due to spam but at the same time the blogger may wish to sent legitimate TBs to other blogs who allow it.