Twitter Acquires MoPub

A lot of premium pubs use direct sold advertising - sign ads directly with large brands (such as P&G, King.com) at a guaranteed CPMs. Also, they sign exclusive deals with ad networks where they promise exposing a portion of their ad inventory in exchange of guaranteed CPMs. Publishers also setup various network waterfalls - stack ranking networks in various countries to determine which network should take a crack at your inventory first, which second and there on. In addition, for remnant inventory (which has no ad network or direct ad sales opportunity), Mopub exposes those to their RTB exchange to get a decent rate for them. Mopub makes all these different types of interactions possible through their product.

Now, in your case, the problem is that you are so small that no advertiser is willing to do a direct deal with you (it is not worth their time considering you are so small). Additionally, no network will do an exclusive contract with you. So your best bet is to mediate between various ad networks and let Mopub exchange take a crack at your inventory while you hope for better CPMs.

Mopub is a great product built by a brilliant team of people. Just because your app is not making money doesn't mean it is bad. If you become big, Mopub CS team will actually contact you to hand hold you to configure your networks in an optimum manner.