Another story idea I might as well throw away, having sat on it since 1990 (had it while reading T.Pratchett's Moving Pictures)...
(Bloody IE crashed and lost this, so this version is terse, sorry)
Postulate a benign galactic civilization. They watch but don't interfere with primitive civilizations. Prime directive, etc, etc.
They're ethical, for values of... never mind.
Postulate that the only basis of currency exchange for any large scale civilization is information.
Postulate that they've solved the digital rights issues for information, and because they're ethical they don't just steal cultural items from primitive cultures but let the credits gained from recordings, or whatever, be held in trust until such time as the civilization becomes sufficiently advanced to join the community.
So, what sort of information would they gather? Or value? The equivalent of popular entertainment? Cultural items? Great plays, works of fiction and the like may translate well and be popular in the rest of the universe. For all we know the whole multiverse is busy watching Neighbours... No, that's going too far. Back to reality...
Following on from that we have the story, a pair of Crysteel and Danstor types arriving at Terry Pratchett's door one night to tell him that because of the popularity of The Diskworld books, translated into a few tens of thousand languages and distributed across the entire multiverse, he now owns roughly half the entire universe and if he doesn't come along quietly and spend some of it the galactic economy is going to crash... Sir.
 Characters from an amusing early Clark first contact from the aliens POV story.