I have a lot of thoughts about this development, but first -- to note it.
The first ads are for Samsung. They don't use Twitter's ad platform. Twitter is sure to object.
A few questions follow from this.
1. How did the AP get 1.5 million followers? Did Twitter promote their feed? If so, it seems Twitter has a legitimate right to the revenue flow from their ad feed. Do they have a contractual right to it?
2. What happens if Twitter shuts them off as they did with developers? What might a shut-off look like when it comes to a content feed? For developers it meant that their API calls were not handled.
3. What do other content companies plan to do here? Do you all think of Twitter as another channel for your content flow? Do you have plans to monetize it? Do you envision your paywall, if you have one, ever extending to your Twitter feed?
4. Why is there a picture of a frog on the AP's Twitter page? :-)
Now, my ready-made answers.
1. Don't put ads in your feed, instead think of your feed as a flow of ads pointing to your content. Put ads on the pages you point to from your feed.
2. Don't depend on Twitter to be a common carrier. They are a media company, like you. You're using a competitor to connect with your readers. This is not a healthy situation.