Evan Stone, a former teacher and founder of a teachers advocacy group called Educators4Excellence, said he was disappointed in what he saw as a lack of leadership on both sides.

WSJ: Teacher Evaluation Deal Falls Apart

It is not clear whether Alwaleed would be buying shares from Twitter cofounders Evan Williams or Biz Stone.

FORBES: Saudi Billionaire Alwaleed Reportedly Interested In Twitter Stake

Goldman previously worked with Twitter co-founders Evan Williams and Biz Stone on Blogger, before the company was bought by Google.

FORBES: Twitter VP of Product Jason Goldman Flies The Coop

Stone is teaming up with Twitter co-founder Evan Williams and former Twitter head of product Jason Goldman to start Obvious.

FORBES: Biz Stone Steps Down From Twitter, Re-Starts Obvious Corp.

Mr. Costolo has been credited with carefully managing the exits of two of the company's co-founders: Evan Williams, who was Twitter CEO between 2008 and last fall, and Biz Stone, Twitter's evangelist and spokesman on talk-show circuits.

WSJ: New Financing Values Twitter As High As $7 Billion