Image source: Sotheby's.

What: Shares of Sotheby's (NYSE:BID) jumped 17.5% in March, according to data provided by S&P Global Market Intelligence, after a bullish billionaire upped his stake in the stock.

So what: Dan Loeb's Third Point LLC hedge fund bought an additional 10,000 shares of Sotheby's to increase his stake to 10.75% of the company late in February. The news hit the market the first day of March, and it was in those first trading days of the month that most of the move took place. 

This isn't a big increase in Loeb's stake on a relative basis, but it shows he's still high on the company. Now, with three board seats, it's time to see if he can turn the business around.

Now what: The problems at Sotheby's in the past year haven't been because it doesn't have enough high profile investors, it's been a slowdown in the high end art market. And Loeb's position, while a vote of confidence, doesn't fundamentally change that fact. I would like to see a material turn around in operations before jumping in following an activist investor. Blindly following big name investors can be disastrous for retail investors, as stock like Valeant Pharmaceuticals and SunEdison have shown over the past year.