The following video is from Monday's Investor Beat, in which host Chris Hill and analysts Jason Moser and Andy Cross dissect the hardest-hitting investing stories of the day.

Yahoo! CEO Marissa Mayer announced that the company has bought Tumblr for $1.1 billion. It's her boldest move yet since joining Yahoo! last summer. Even though she promised "not to screw it up," the Tumblr acquisition has some wondering if Yahoo! paid too much. In this installment of Investor Beat, our analysts discuss the pros and cons of this deal, as well as taking a look at four stocks that made big moves on Monday's market, and two stocks they'll be watching closely in the week ahead.