Late last week, co-founder Biz Stone sent an email to news outlets informing them of changes to Twitter's Terms of Service.
An overview appears on Twitter's blog; but in short, they follow thus (from the blog):
Advertising—In the Terms, we leave the door open for advertising. We'd like to keep our options open as we've said before.
Ownership—Twitter is allowed to "use, copy, reproduce, process, adapt, modify, publish, transmit, display and distribute" your tweets because that's what we do. However, they are your tweets and they belong to you.
APIs—The apps that have grown around the Twitter platform are flourishing and adding value to the ecosystem. You authorize us to make content available via our APIs. We're also working on guidelines for use of the API.
SPAM—Abusive behavior and spam is also outlined in these terms according to the rules we've been operating under for some time.
A recent survey found that porn spammers are increasingly deserting email in favor of more aggressive tactics on sites like Twitter, where spam followers have become a problem of greater seriousness as the site's popularity increases.
Apropos to advertising, the Terms specifically read: "The Services may include advertisements, which may be targeted to the Content or information on the Services, queries made through the Services, or other information" — leaving the metaphorical door ajar for marketers to potentially target users based on relevant desires of the moment.
For example, one user craving a hamburger could be offered a coupon from a nearby hamburger purveyor.
The section concludes, "We're leaving the door open for exploration in this area but we don't have anything to announce."