Do you remember back in January when news came out that Twitter users would be able to create two types of self-serve ads (promoted tweets and promoted accounts)?

Twitter is now testing self-service ads with some of its existing advertisers. This allows them to run their own promotions and pay with their credit cards.

This was revealed by Twitter Chief Revenue Officer Adam Bain at a Business Insider conference:

(He also says some other interesting things about Twitter advertising. For example, he discusses a successful campaign for Paramount for the movie Super 8. He wouldn’t say how much they made, but he did at least say that they knew what they were paying up front, as opposed to that being based on ticket sales).

“Self serve has materialized for a handful of these businesses now that are testing with us this year,” he said. “We’ll continue to learn and scale that out over the next bit.”

Regarding the self-service ads, Twitter’s Matt Graves is quoted as saying:

This is an important step in continuing to grow Twitter’s business. Our Promoted Products can help small and medium-sized businesses build their audience on Twitter and better engage with the people they want to reach.

As with all of our advertising efforts, we’re starting small, testing carefully and making improvements as we learn what works. We will slowly roll this capability out to more advertisers in the coming weeks and months.

This could be the beginning of the real moneymaker from Twitter. It could also be the beginning of a lot more people bitching about ads on Twitter.