Josh Constine writes:

Now there’s 78 million Americans age eighteen and older who use Facebook mobile, and they spend 7.3 hours per month there on average, compared to the total 160 million Americans who use Facebook and spend an average of 6.5 hours on its website per month. That’s a big shift from when the web was king.

Facebook realized it had to start making money on mobile, but people hate traditional mobile ads. CEO Mark Zuckerberg didn’t want annoying banners that took up most of your Facebook screen. so Facebook’s solution was mobile Sponsored Stories –- stories in your news feed that could appear there anyway, but that companies pay to have appear more prominently and frequently.

Time spent on Facebook’s mobile site and apps per month (441 minutes) has finally surpassed usage of its classic website (391 minutes) — for Americans who use both Facebook interfaces according to the latest report from comScore.

Yet another reason why the Instagram purchase was important.

Mobile is the future.