Twitter’s strategy around monetization can be summed up in three words: “take it slow.

Thanks to hundreds of millions of dollars in funding, Twitter has been able to do something many digital media upstarts can’t: explore new ad models at what often seems like a snail’s pace, working primarily with a select number of brand advertisers and agencies.

From Promoted Trends to Promoted Tweets, the company has been somewhat creative in how it monetizes its impressive audience. After all, it could have easily taken a more aggressive approach, tossing up ads at the expense of the user experience.

But it does appear that Twitter is getting comfortable enough with its Promoted ad offerings it has developed to finally put advertisers in the driver’s seat.

As reported by AllThingsDigital’s Peter Kafka, Twitter is allowing some of its advertisers to set up their own ad campaigns:

It’s still just in test mode, and only open to a handful of advertisers. But those who can use it can now buy ads directly via Twitter, using a credit card and a Web browser, without ever having to talk to a human being.

Right now buyers can only purchase some of Twitter’s ad products — specifically “promoted accounts” and “promoted tweets” — but Twitter says that will expand over time, as it rolls out self-serve to more buyers.

As Kafka notes, a self-serve ad offering has reportedly been in the works for a while, but now that one is actually in the wild and confirmed by Twitter, it signals a new phase in Twitter’s evolution.

Although much has been made in the past about non-advertising based business models Twitter could adopt, it’s quite clear that the company is going to rely heavily, if not primarily, on ads. And the only way it’s realistically going to sell enough of them to live up to the expectations of its investors is to allow advertisers to buy them in a self-serve fashion.

The big question now is whether those advertisers, left to their own devices, will be able to turn their Twitter ad buys into ROI. Earlier this year, several reports had marketers calling into question the efficacy of Twitter’s ads.

If Twitter’s self-serve offering is to thrive, a la, say, Google AdWords, it will need to make sure that its advertisers have good reason to keep serving themselves.