Why did Yahoo! make this acquisition? We know very little about Marissa Mayer’s big goals for Yahoo!, but we know one. She wants Yahoo! to own users’ daily habits. At an analysts conferece recently, she classified these as “searches on the Internet, checking finance, doing your email.” Yahoo! is skating to where the puck is going to be when it comes to “daily habits.” The Tumblr daily dashboard is a daily habit, and by some accounts, moreso than even Facebook or Twitter among teens.