The company has shuffled its executive team, and CEO Dick Costolo has faced heavy criticism for the state of the company, his management style, and most recently, his decision to sell shares. A strong offer from another tech giant -- perhaps a company looking to crack into social media -- would be difficult to turn down. Despite the uncertainty over Twitter's future -- it doesn't appear as though it will ever be as large as Facebook -- the company has a unique business model, and a strong moat.