Is the Android Marketplace noticing a large overlap between those who download Grindr and those who install Sex Offender Search?
This seems unlikely given their two very different target audiences.
The last question -- what harm are such associations doing -- is more complicated to answer.
Associations like those listed in the Android Marketplace (or Apple's Genius system, Amazon's recommendation engine or Bing's search suggestions) can be starting points for good conversation or chilling silencers of individual expression and community identity.
To answer the first question of who made this association between Grindr and Sex Offender Search: it is those who design and maintain the Android Marketplace, the Droid's version of Apple's App Store.
To be fair, Apple has had its own struggles deciding what kinds of apps to sell: for a while it rejected a cartoon app created by Pulitzer Prize-winning Mark Fiore because it "ridiculed public figures"; and it recently deleted an app designed by a religious group to "cure" gay people.
But we're far from fully understanding the ethical obligations that Apple, Google and others have when their platforms act as de facto regulators of free speech.These can be great opportunities to debunk bad thinking that would otherwise go unchallenged.