You have no idea how mobile advertising works. Unlike what you may think, mobile advertising is not a magic wand where you integrate an SDK and viola you make shit ton of money. In your post you are criticizing Mopub for not making you money when the problem may be in your app and its popularity.
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.
Chill out ! I never said it doesn't work for ANYONE. We actually got introduced to MoPub by Daniel from Mag Interactive (the folks behind Ruzzle) and they were very happy about it. They have millions of users and as you said, they can negotiate better terms with some advertisers and make some revenue.
For us (and we're not that small...> 400.000 downloads) it's not significant. And we are more popular than the majority of apps on the App Store.
Have you developed a mobile app that makes a lot of revenue ?
