Mainstream companies are increasingly choosing to use Twitter as a communication tool, which especially poses a threat to social networking sites MySpace and Facebook, which over the past year have worked to gain interest from companies as communication platforms, paidContent reported Monday.

For example, BusinessWeek, SalesForce.com and Best Buy have all incorporated Twitter feeds into their own Web sites and customer relations activities, according to paidContent.

BusinessWeek is adding a Twitter feed to the social networking site it launched last summer, Business Exchange. The addition marks a first among businesses who have gone directly to Twitter, without first using Facebook, paidContent reported.

Best Buy has made a similar move with its new social media hub, ConsumersPrice.com, and Salesforce.com has also integrated a Twitter response tool into its customer relations product allowing service representatives to monitor Twitter streams for messages that mention its brand.

The surge of new business comes as Twitter celebrates its third anniversary. The company is also celebrating the potential revenue it may start generating, thanks to a sponsorship deal that Federated Media brokered with Microsoft, according to paidContent.