What you need to know – 05/19/11

Amazon has expanded its trade-in program, which lets customers trade in an item in exchange for an Amazon gift card, to include electronics.

The company also launched its fifth publishing imprint, Thomas & Mercer, a mystery and thriller category that joins Amazon’s other imprints, including the newly launched Montlake Romance, AmazonEncore, AmazonCrossing, and The Domino Project.

Online events and ticketing site Eventbrite raised a $50 million Series E round of funding led by Tiger Global with participation from several other firms.

Gilt Taste launched in beta as the artisan food branch of Gilt Groupe.

Sophia.com, an online social learning platform, acquired Guaranteach.com, an online math learning resource. The terms of the deal were not disclosed.

Jibe, a site for finding jobs based on your social connections, raised $6 million in Series A funding led by Draper Fisher Jurvetson and DFJ Gotham with existing investors, Polaris Venture Partners, Zelkova Ventures, Lerer Ventures, Thrive Capital and Stanford University Endowment participating in the round.

LinkedIn has exploded out of the gate and as of 10:53 am EDT, its share price is up 96% to over $88.

Mark Goines, famed for his angel investments in high-growth companies like Mint, BabyCenter, and Practice Fusion, joined Morgenthaler Venture’s IT team at its Menlo Park office.

Saygent, a voice response and analysis SaaS, raised $1 million in seed funding from 500 Startups, Innovation Endeavors, Juvo Capital and more.

Twitter rolled out some API changes that gives users more oversight when granting third-party applications access to their account, but it’s already proving to be a headache for developers of those apps.

Zynga acquired Casino City developer DNA Games. Founder and CEO Jonathan Lee is now General Manager at Zynga.