eMarketer predictsthat mobile advertising across all principal formats -- display, search andmessaging-based -- will reach $1.56 billion by 2013.

Commensurate with its status as an emerging channel, mobile advertising willachieve a lofty compound annual growth rate (CAGR) of 37.3 percent between 2008and 2013 -- considerably higher than online ad spending as a whole, but more inline with emerging online formats such as digital video.