BlackBerry is setting modest goals for the smartphone maker's U.S. prospects as its new flagship device, the BlackBerry 10-powered Z10, makes its debut in the U.S. today on AT&T for $200 before Verizon Wireless' scheduled launch next Thursday. "Our objective and that of our carrier partners is that very quickly we emerge as a strong No. 3," says Frank Boulben, BlackBerry's chief marketing officer. Boulben has prepped the company's largest campaign ever for the Z10, which already has been unveiled in several markets overseas. BlackBerry 10's mobile application store has reportedly reached 100,000 apps.