Online advertising has been predicted by eMarketer to reach $50 Billion in 2015. By contrast the total spend in 2010 was $26 Billion. Comscore had shown that in the last two months of 2010 alone there was over $32 Billion spent online. Therefore it would be no surprise that over the course of an entire year $50 Billion may be spent 4 years from now.
Sales online have been increasing consistently every year as has advertising online. Take a look at eMarketer for more online research.