* Fortune’s annual Brainstorm Tech conference kicks off later this afternoon with the day’s speakers including Twitter CEO Dick Costolo, Dreamworks Animation CEO Jeffrey Katzenberg, Square COO Keith Rabois, and Stephanie Tilenius, Google VP of Commerce and Payments. Keep checking the Web site throughout the day for the latest coverage.

* Yep, you read that headline right: Borders is closing its remaining 399 stores and laying off 11,000 employees after failed negotiations. Said Borders Group President Mike Edwards in a statement: “We were all working hard towards a different outcome, but the headwinds we have been facing for quite some time, including the rapidly changing book industry, e-reader revolution, and turbulent economy, have brought us to where we are now.” (paidContent)

* Liz Gannes over at AllThingsD sifted through Zynga’s S-1 addendum and walked away with a few revelations, including exclusivity start dates for various games, Facebook’s consent to help Zynga meet “certain growth targets for monthly unique users,” as well as an agreement to sell ads next to Zynga games and share a redacted portion of those ad sales with the casual gaming juggernaut. (AllThingsD)

* Cisco will lay off 6,500 workers, or roughly 9% of its workforce, in an effort to save $1 billion in annual costs. (Tech Trader Daily/Barron’s)

* Amazon introduced Kindle Textbook Rentals, a rental service promising to save students a huge chunk of cash — up to 80% off the print list price, according to the company. Students can choose anywhere between a 30 day and 1-year rental period,  and Amazon says it’ll have “tens of thousands of textbooks” available to choose from. (Amazon and Gizmodo)

UPDATE: Facebook responded to All Things D’s report with a statement. “We don’t have agreements with any developers, including Zynga, to share revenue from ads next to their Facebook canvas apps,” said a company spokesperson. “We did agree with Zynga to work together in the future on providing ads on their properties beyond Facebook, but we have no current timeline for when we might start working on that.”

Don’t miss the latest tech news. Sign up now to get Today in Tech emailed to you each and every morning
.