FOR Business. Cambridge, MA 9/24/2012 Jack Dorsey, right in black, speaks with a group of students next to the food trucks that use his product, Square. Dorsey often recruits by speaking to students in informal settings. Jack Dorsey, co-founder of Twitter and the mobile payment start-up Square, comes to MIT on Monday to pitch his mobile payments company in Cambridge, MA on Monday, September 24, 2012. (Yoon S. Byun/Globe Staff) Section: Business Slug: 25square Reporter: farrell LOID: 5.0.2908915579