So let’s say instead of trying to ‘create a consistent experience,’ Twitter charged users $10/yr to use 3rd party clients. The idea being when you try to auth against a client, Twitter checks to see whether you’re activated for offsite tweeting. You can’t compose messages, RT or receive/send DMs without authing in, and a 3rd party client that lacks the ability to send Tweets likely wouldn’t gain much traction, so don’t worry about their read access of the API.
This is not unlike what Instapaper does. If you’re a paying customer, you get to authorize your own API access for third-party clients/services. It’s smart, but I’m not sure it would be smart for Twitter. I suspect the revenue generated would not outweigh their core desire for more control over the entire experience.
I think they would view it as chopping off an arm to make a headache go away.