News Corp. executives often present MySpace and Facebook as competing in different markets, with Facebook used as a communications vehicle and MySpace for entertainment. Whatever the case, a straight line can be drawn between more time spent on Facebook and less on MySpace.

According to new figures from Nielsen Online, total minutes spent on Facebook in April rose 699 percent from a year ago. At MySpace, meanwhile, total minutes spent fell a jarring 31 percent.

To be sure, MySpace remains a popular draw, with users spending 83 million minutes on the site in April. Yet, that's now a fraction of the total spent on Facebook, which drew triple the amount of user time.

Nielsen Online, which shares a parent company with Billboard, also charted the stunning rise of Twitter. The total time spent on the site rose 3,712 percent to nearly 5 million hours in the past year. Those figures only include visits to Twitter.com, not the use of the many third-party Twitter applications employed to read and respond to messages. Twitter now ranks as the No. 4 social network in terms of time spent, according to Nielsen.

Nielsen analyst Jon Gibs said that MySpace's reversal of fortune shows the fickle habits of online consumers -- a cautionary tale for all players.

"One thing we know about social media is it always changes," he said. "The past five years have been an evolving process starting with Friendster. We know it'll continue to change and evolve. The market we see right now is by no means a stable market. We expect new entrants."

Social networking as a whole has been on a roll, according to Nielsen figures. Total time spent on social networking sites increased 81 percent compared to a year earlier.

There is one area where MySpace continues to trounce Facebook: video. In April, it served triple the number of video streams compared to Facebook, ranking by far as the No. 1 social network for such viewing activity.

"We've seen MySpace shifting its focus to being much more of an entertainment portal with social media aspects rather than a social media hub," said Gibs.

News Corp. has reshuffled management at MySpace. It brought in former AOL chief Jon Miller to lead its Internet efforts and former Facebook exec Owen Van Natta to serve as MySpace CEO.