Chart - US Mobile Ad Spending

Following explosive entrances by Facebook and Twitter to the marketplace, as well as a strong performance from Google, US mobile advertising spending grew 178% last year to $4.11 billion, according to a new forecast by eMarketer, and spending is expected to rise a further 77.3% to $7.29 billion in 2013.

That’s a nearly fivefold increase in spending since just 2011, and includes ad dollars spent on display, search and messaging-based formats served to all mobile devices, including tablets. By 2017, eMarketer projects US advertisers will devote $27.13 billion to mobile—just under 45% of all digital ad spending and 13.8% of total media ad spending that year. Read the rest at eMarketer.