IBM, Twitter Plan Talks on Patent Dispute - Digits - WSJ

Also see Twitter Raises Sights in Heady IPO Market (WSJ) and In “Hatching Twitter,” a Billion-Dollar Company That Almost Wasn’t (AllThingsD)

"Based upon a preliminary review of the patents, Twitter said in the filing that it believes it has “meritorious defenses to IBM’s allegations.”
Twitter said in filings it has nine U.S. patents as of Sept. 30 and 95 U.S. patent applications pending – relatively few for a technology company. By contrast, Facebook Inc. said it had 774 U.S. patents before its IPO last year.
Twitter employs an unusual intellectual-property strategy, under which employees retain the rights to their inventions, rather than assigning them to the company, as is the common practice. The policy says in part that Twitter can’t pursue offensive litigation without the inventor’s permission."

IBM, Twitter Plan Talks on Patent Dispute - Digits - WSJ