A new Nielsen Company study on Internet and mobile Internet use says e-mail is still what Americans spend the most time doing on their mobile phones.

Visiting portals is the second most time-consuming mobile behavior, followed by visits to social networks/blogs.

The report, which was released today, had some bad news for mobile journalism:

"Other mobile Internet activities seeing significant growth include music and video/movies, both seeing 20 percent plus increases in share of activity year over year. As these destinations gain share, it's at the cost of other content consumption -- both news/current events and sports destinations saw more than a 20 percent drop in share of U.S. mobile Internet time."

This may mean it's important to keep up your e-mail newsletters, and to make sure they're mobile-friendly.