Social networks provide a ripe ground for advertising, and somehow Twitter has managed to avoid tailored ads for some time now. That appears to be changing in the future, as cookie-based ad delivery will soon be tested on Twitter.
The new tailored ads will be initially tested in the U.S.; if successful, they could expand to other markets. In all probability, this type of advertising will be more profitable for the company, though it's controversial all the same, as similar tactics have raised concerns about privacy in the past.