Customers love Cognizant's C2 platform so much that they want to buy it. Too bad it isn't for sale.

Cognizant Technology Solutions, a tech outsourcing and consulting firm that serves huge companies, has built a corporate version of Facebook that pulls together a bunch of Web 2.0 tools such as Twitter feeds, employee-written blogs, and chat. It's the kind of collaboration tool many businesses say they'd love to have. But Cognizant isn't peddling the product to clients; the company instead uses its homegrown social-networking platform, Cognizant 2.0, to share ideas and communicate internally -- and it gives customers access to the site so that they can post queries or search blogs and read tweets (called "Cweets") for answers to frequently asked questions.

Such high-tech customer service helps explain why Cognizant (CTSH), based in Teaneck, N.J., has been growing like crazy.