TuneIn, a Web service that lets you listen to radio shows and podcasts from all over the world, for free, says it has 50 million users. But it would like many more, and it would like them to do more stuff when they visit.

So here’s a format change aimed at accomplishing that. TuneIn is trying to present itself as a social network, a la Facebook and Twitter, except that instead of your kids’ pictures, or updates about your breakfast cereral, you share your favorite radio stations.

TuneIn users can also “follow” stations and genres of stations. And starting today, they’ll find that if they’ve “favorited” stations in the past as a way to bookmark them, those favorites are now follows. Which means some stations will find they have more “followers” on TuneIn than they do on other networks.

In any case, just calling yourself a social network doesn’t mean that users are going to treat you like one. And while there are some very successful examples of social networks designed for a specific purpose — see Instagram — others have struggled, usually because that activity is already happening on Facebook or Twitter — see all the “second screen” talk-about-TV apps.

If it does work, then perhaps CEO John Donham will achieve his goal of attracting “hundreds of millions” of users. And if that happens, then TuneIn will have a better shot at generating real revenue, which is an issue for the company so far.

That’s because in most cases TuneIn, which wants to make money from advertising, doesn’t have the right to sell ads in any of the audio streams that people access from the service — it essentially acts as a Web browser that points people to the source of the streams.

That means TuneIn’s operational costs are low, since it’s not creating or hosting content. But its top line isn’t very big, either.

But TuneIn can sell ads on the pages that help guide people to those streams. So if it gets users spending more time on the site and its apps, to talk about stuff they like, and see what other people like, then that will generate more opportunities to get marketing messages in front of their eyeballs.