Starbucks and Best Buy are the first retail advertisers to take advantage of Twitter’s new "Promoted Tweets" form of search ads, as reported by MarketingVox, an online marketing news journal.
As of 13 April 2010, searchers will see a single ad appearing at the top of a search. The ads are first appearing only in search results, but will appear later on in user feeds on the main Twitter site.
(Source: Retailer Daily)