In case you missed it, Twitter rolled out some in-line text notices on their web application today.
The rollout has tweeters all a-flutter (and advertisers salivating) that it might be a sign they are about to introduce some type of monetization model like Ad-Words style pay per click advertising on the site.
Read more over at my SiteProNews blog: Is Twitter Testing Ads?
UPDATE: Yes, Twitter WAS testing ads. Cha Ching!