(Mobile and social media are small—but getting bigger.)
Digital advertising has been the bright spot in many ad spending forecasts, and that trend is slated to continue.
In the "Five-Year Interactive Marketing Forecast Report," Forrester Research projects a 17% compound annual growth rate (CAGR) for US interactive marketing spending over the next five years, to nearly $55 billion in 2014.

As it grows, interactive marketing will represent an ever greater portion of US advertising spending. Pegged at 12% of the total in 2009, interactive ads will represent 21% of all Ad spending in 2014.
Though both starting from a small base, Forrester predicts social media and mobile marketing will grow fast. Social media marketing will experience a 34% CAGR, with mobile not far behind at 27%.
Search marketing makes up more than one-half of all interactive dollars, and will remain the biggest format through 2014. Search is expected to grow by a 15% compound annual rate.
According to eMarketer estimates which exclude spending on mobile and social media, search advertising also makes up a majority of UK online advertising spending. Search spending will climb slowly this year, at just under 5%, but 2012 will see a return to double-digit growth.