From here forward, only Twitter, the company, will be allowed to sell ads posted to Twitter, the microblogging service. Twitter wants to avoid crass commercialism and shilling. Too late, guys.

In a blog post, Twitter COO Dick Costolo (pictured) said the company would ban third-party advertising in tweets, meaning the only way to place tweet-stream advertisements will be to buy "promoted tweets" from Twitter Inc. This decision means more money for Twitter, but Costolo couched it in terms of quality:

Third-party ad networks are not necessarily looking to preserve the unique user experience Twitter has created. They may optimize for either market share or short-term revenue at the expense of the long-term health of the Twitter platform. For example, a third party ad network may seek to maximize ad impressions and click through rates even if it leads to a net decrease in Twitter use due to user dissatisfaction.

Of course, this policy won't end outside advertising on Twitter. The network will still be rife with stealth spam of all sorts, from self promotion to log rolling for friends to paid tweets. If anything, that sort of marketing will only go up. It will just be harder than ever to identify. Oh, Twitter.