My the community choosing which apps are valid, it encourages the free-market to build good app.
Did you miss the point about two-factor authentication for doing the upvotes. So, you would have to do a "I am human" action after you click upvote in order for the upvote to go through.
Oh a captcha-unfortunately their are programs that bypass that. It be like like adnetwork vs adblocker. But it would make it very very costly for bots to use it. Plus you can do a POWCAPTCHA+I am human captcha hybrid service to enhance the feature. And I guess community apps voting will work. But how many upvotes will it need to be active. Or will be like voting on apps=bandwidth can use. More Votes on app=more bandwitch
Have you seen Binance's slider?
If there has to be a percentage votes from the community for approval, that might encourage developers to promote their app more. And then we probably should see a percent usage from the apps too, which could be handled by keeping track of which app submits the entry.
Honestly, at first I preferred to restrict upvoting to only Steemit, but apparently people cried about it not being decentralized. So, that's why I suggested approved apps and community voting. However, the proof is in the pudding and things are never really decentralized on a social media app, so I say, that it should ONLY be Steemit with upvote ability and 2FA for verification.
2fa isn't only captchas. Replying to a text with the code in it to be able to vote would be a pain, but it would eliminate bots without their own phone.