Big-name and -money advertisers have hitherto been reluctant to put much money into web advertising, but that trend is reversing fast, according to eMarketer, a leading advertisement tracker.

In 2006 the top 100 advertisers cut their spending on TV, radio, and print by $230 million and raised their online ad spending by $558 million—an increase of approximately 17 percent.

According to the New York Post, that trend is expected to continue:

Emarketer expects the Internet’s share of total ad spending to climb from 7.4 percent this year to 13.3 percent in 2011.

In that same period, online spending will roughly double, rising to $42 billion from $21.4 billion.

In 2006, "more than half of the biggest advertisers cut spending on traditional media while boosting their online ad budgets, eMarketer senior analyst David Hallerman wrote in the report," the Post notes.

Although this could be seen as a bubble or fad on the part of big companies, it almost certainly is not, instead reflecting a real restructuring of the U.S. media that the advertising money is simply following and confirming. If anything, big advertisers have been slow to acknowledge the change, and the underlying movement to the Internet as a central medium of communication is probably even stronger than these numbers suggest.