How big is email advertising?

It’s big and attractive. This year (2007), $1.2 billion was spent on Email advertising, and is projected to grow to $2 billion by 2012.

However, advertising through opt-in lists may not be ever-attractive. While 25% of all email delivered is for opt-in email lists, 40 percent of unsubscriptions from opt-in lists are because of subscribers being sent too many offers.