• Microsoft is suing Barnes & Noble
  
  — alongside Foxconn and Inventec — over alleged patent infringement, including “features” in the Android operating systems on which its Nook eBook readers are based. Things like window tabs, status bars, and showing the content of a page while it’s still loading, are included. (Fortune)
• Another lawsuit is brewing, but this time it’s Apple after Amazon. The Cupertino company requested a judge’s order to prevent the popular e-marketplace from using the “App Store” name as well as for unspecified damages because of Amazon’s use of the term. “Amazon has begun improperly using Apple’s App Store mark in connection with Amazon’s mobile-software developer program,” Apple’s complaint read. (Bloomberg)
• So what happens if the much-talked about AT&T acquisition of T-Mobile doesn’t go through? Ina Fried of AllThingsD got to the bottom of that scenario and discovered T-Mobile walks away with $3 billion as a “breakup fee,” some Advanced Wireless Spectrum (AWS), and some sort of roaming agreement to be determined by the two parties. But don’t take our word for it. Check out Stephen Colbert’s succinct take on all things AT&T. (AllThingsD)

[youtube=http://www.youtube.com/watch?v=rsCp-1hgfxI]

• Facebook’s valuation just hit another all-time-high. Thanks to an auction of shares via SharesPost, the company is roughly worth $85 billion. (TechCrunch)
• Twitter celebrated its fifth anniversary with this star-studded YouTube video with plugs from Secretary of State Hillary Clinton, House Speaker John Boehner, Martha Stewart, tennis athlete Serena Williams and Snoop Dogg — yes, Snoop! — explaining the social network’s more meaningful uses.

[youtube=http://www.youtube.com/watch?v=4AN4_N5N52U]

• Sprint announced it will sell a 4G version of the Samsung and Google Nexus S smart phone this spring as well as full Google Voice integration with each and every mobile number at no additional cost to subscribers.  (Los Angeles Times)
• Meanwhile, Google gets another endorsement, though this one’s from young professionals. Apparently one in four surveyed recently want to work for Google, nearly twice the number who selected Apple as their ideal workplace. (Wall Street Journal)
• Reddit owner Conde Nast is contemplating spinning out the rapidly growing social news site. While the publishing powerhouse would still own it, it would sell a stake at a potential $200 million valuation. (AllThingsD)