AT&T announced it would no longer offer unlimited data plans for new users of smartphones like the iPhone. Some people simply use too much data. AT&T says they will offer a tiered plan, charging $15 a month for 200 megabytes, or $25 for 2 gigabytes. (Existing customers can keep their plans.) The company says the bigger plan would cover downloading 400 songs, watching 1,000 video minutes, or a million single-page emails, more than enough for the average user. Analysts say the announcement could signal the end of simple all-inclusive data plans. Use of mobile data has skyrocketed: In April, 57.1 million Americans had unlimited data plans, up 57 percent from a year ago. AT&T has suffered more from data hogs, thanks to the iPhone, whose users soak up a third more data than the average smartphone user.