* Facebook countered Yahoo’s (YHOO) lawsuit with a lawsuit of its own, spanning 10 patents covering areas like homepage, photos, and ads. (Friending Facebook Blog)

* Instagram, the popular photo-sharing app with over 30 million users, just officially arrived on Google’s Android operating system. (TechCrunch)

* Up to 2,000 Yahoo employees could be laid off later today in nearly every unit, with the products division expected to be the worst hit. (All Things D)

* Amazon (AMZN) is reportedly testing a service that will let Kindle Fire users buy items and subscriptions via mobile apps. In return, the company will take a 30% commission. Such a move would help Amazon remain competitive with Apple (AAPL) and Google (GOOG), which already have similar services in place. (Bloomberg)

* How Apple could become the first $1 trillion company. (Fortune)

* Meet the iBrain, a small device that could allow people like physicist Stephen Hawking to communicate simply by thinking. (The New York Times)

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