The music industry has a long, long history of people paying to put songs in prominent places. If you built it yourself you would be 100% confident that nobody was paying the person compiling the playlist to put songs on it.

Well, at least at first. If your playlist derived from the ambient music of a particular streetcorner in Berlin becomes popular enough, someone would probably try hanging out there blasting their new song 24/7. Someone else might try approaching you about working out a deal to pay you to slip their new song into the mix. And of course you can never know who's paying to put songs on whatever stations or playlists the locals are listening to.

Some pretty interesting things would probably happen as the result of your goofy little fun project getting big enough to start having these problems though.

What more could one possibly need than "it'd be fun to build"? Does everything in the world have to be novel and important? Or can some things just be cool and for fun?