Dr Blobel hypothesised, and then proved, that each of these location-specific proteins is created with a tag that tells it where to go or, rather, latches on to the place it is supposed to be in when it gets there.
For instance, you can not only list your employer, you can list the specific projects you worked on and even tag colleagues who worked on them with you. (My colleague Kashmir Hill notes that the new Facebook is like the professional social networking site LinkedIn now.) Bad, because you may not want to give Facebook any more information on you than it already has.