Also - I don't see the publisher's willingness a risk factor if the product, service or brand you want to promote is a relevant one for app user base.
If you're curating for your idea of quality, you're controlling which ads publishers can display where. This isn't a bad thing; it's how virtually every ad network operates. But then what's different about this approach?
The risk factor is that with a traditional ad network, I know I'm buying a certain number of impressions in a certain period of time, with analytics. But if inventory is doled out whenever my publisher partner (or their algorithm) feels like it, then my holiday promo campaign is a crapshoot and I might have wasted both money and (worse) time. I'd pay a premium to get rid of this risk.
I feel like the TinyAds network is more about buying influence and exposure and not a fixed number of impressions (that basically translates to the number of times an ad was loaded and that's it).
Also - I'm not sure why would you think your inventory is doled out since the app publisher accepted your ad and you have the guarantee of the ad being displayed on their app?
With this network - if an advertisers wants to buy an ad slot - but you don't agree with the product or service for some reason you're just going to decline the ad.