* Google (GOOG) chairman Eric Schmidt told the U.S. Senate antitrust committee that the iPhone 4S’s voice assistant, Siri, poses a “competitive threat” to his company’s business. Confessed Schmidt: “Apple’s Siri is a significant development — a voice-activated means of accessing answers through iPhones that demonstrates the innovations in search.” (Apple Insider)

* Barnes and Noble (BKS) is holding an event this morning in New York City where the retail chain will reportedly unveil a hardware update to its Android-based, reading focused Nook Color tablet. Stay tuned for updates.

* An insightful profile of LinkedIn co-founder and venture capitalist Reid Hoffman, who The New York Times dubs “the start-up whisperer of Silicon Valley.” (The New York Times)

* Meet Tristan Walker, Foursquare’s head of business development and one of technology’s most prominent African American executives. (CNNMoney)

* Instagram co-founder Kevin Systrom on international expansion and funding rumors. (TechCrunch)

* Lessons from 12 New York entrepreneurs after a year in the business. (The Next Web)

* Google’s patent counsel Tim Porter on why the patent system is broken. (The San Francisco Chronicle)

* How online innovators are disrupting education. (Harvard Business Review)

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