The following video is from Thursday's Investor Beat, in which host Chris Hill and Motley Fool analysts Tim Hanson and Matt Koppenheffer dissect the hardest-hitting investing stories of the day.

Activist investor Dan Loeb holds a 9% stake in Sotheby's, and is now calling for the auction house's CEO William Ruprecht to step down, bringing the stock up to a two-year high. In the lead story on today's Investor Beat, Tim and Matt take a look at Loeb's case and activist investor trends on the whole. They also share their thoughts on whether Sotheby's is a buy, sell, or hold at today's prices.

Also, our analysts take a look at four stocks making big moves today. Tesla Motors continues to fall after one analyst's downgrade and the release of an Internet video of a Model S on fire. Constellation Brands rises after great second-quarter earnings news and raised guidance for the full year. Angie's List is down after it slashed prices by 75% in key markets to bring in new members. And Herbalife falls as billionaire hedge fund manager Bill Ackman reduces his short bet on the stock.

And finally, Tim and Matt discuss why they will be watching shares of Costco and Wells Fargo very closely this week.

Chris HillMatt Koppenheffer, and Tim Hanson have no position in any stocks mentioned. The Motley Fool recommends Sotheby's. It recommends and owns shares of Costco Wholesale, Tesla Motors, and Wells Fargo and has the following options: long January 2015 $50 calls on Herbalife. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.