[busymom0]

They could state in their terms of services that the API key will only be valid if the developer doesn't hide the ads.

[iamatworknow]

Then why would I as a developer bother with it at all? I don't want to serve ads someone else is getting paid for from my app. And if my app was to be funded by ads, then what? Display twice the number of ads to the user?

[ceejayoz]

Tweetbot is a paid app. Its revenue model wouldn't be fundamentally affected by Twitter putting ads in the feeds it displays.

I'd rather see ads in my feed than Twitter continue to make third-party clients less useful.

[thinkloop]

Or Twitter could share the ad profits a la YouTube to incentivise all kinds of innovative niche ui's. 3rd parties are not the enemy to be managed. They are a blessing - free engineers who managed the impossible of building a product with customers and traction. UI is a cost for Twitter.