Time Warner’s long corporate nightmare is almost over. It announced that it would dump AOL by spinning off the onetime new media giant as an independent company by the end of the year.

The 2001 merger of AOL and Time Warner, a deal valued at $124 billion, was hailed as the marriage of new media and old media with trendy new media in the driver’s seat. It was a short trip.

The dot-com bubble burst. AOL’s stock turned out to be greatly overvalued, its business model in decline and, moreover, the two corporate cultures grew to detest each other.

Time Warner’s CEO, Gerard Levin, was gone within the year; AOL’s CEO and co-founder Steve Case a year after that.

In 2002 the new company posted a loss of just under $100 billion, then the largest loss in U.S. corporate history.

Time Warner will concentrate on its old media empire — movies, cable TV networks and magazines. AOL will concentrate on its not-so-new-anymore media — Web sites, online advertising and Internet access.

A company that once could buy Time Warner for $124 billion is now valued at between $5.5 billion and $6.5 billion. The spectacular overreaching by AOL and the almost willful blindness of investors should have taught us something about speculative bubbles. Our present predicament with housing and credit shows that it did not.