Twitter expands ad platform with 10,000 more businesses

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Twitter moved one step up from its beta self-serve ad testing today and will now allow tens of thousands more self-serve ads on its site, according to Ad Age.

In a new promotion with American Express, Twitter will let AmEx cardholders and merchants who accept AmEx buy ads on its site. American Express will supposedly give each buyer a $100 advertising credit to get started placing ads on promoted tweets and accounts.

In December, Twitter announced it would start testing self-service ads with about 100 advertisers. The aim, Twitter said, was to make it easier for small- and medium-size companies to advertise by offering the self-serve option for its ad platform. Now the social-networking site is opening this option up to more advertisers, in groups of 10,000.

Twitter seems to be taking notes from Google and Facebook, both of which also launched similar advertising platforms. According to Ad Age, Twitter has sold ads to 3,000 marketers so far and that number should increase if the self-serve AmEx plan goes well.

According to Emarketer, Twitter's ad revenue was $139.5 million in 2011 and is expected to grow to $259.9 million this year.

Ads for the first group of 10,000 businesses will go live on Twitter in March, according to Ad Age, and at some point the American Express exclusivity will end and the platform will become even broader.

CNET's Charles Cooper contributed to this report.