This year about 11% of marketing spending will go to social networks. Borrell predicts that number will grow to one-third of such spending by 2015, representing $38 billion.
And the ratio of promotional spending compared to advertising spending across social networks will increase --- from about 1:3 today to about 1.75:1 by 2015. In other words, $1.75 in promotion will be spent for every dollar in advertising across social networks within five years, Borrell suggests.
Borrell notes, though, that it's difficult to measure the scope and effectiveness of such spending, and that firms use their social networks as a mass medium instead of one that needs targeting.