IPG’s McCann-Erickson has formed Tag, a unit that will develop strategies targeting 18- to 24-year-olds. Leading the division are Lori Senecal, the New York shop’s evp, director of account management, and svp, group creative director Craig Markus. Tag will serve existing clients, including Interbrew, the maker of Rolling Rock, and Microsoft. It will also pursue new clients that are targeting young adults.