Luxor Capital, run by Christian Leone, rarely files a 13D, but often takes very large positions. They own several restaurants, including BJ's (BJRI), which they have had in depth conversations with management and the stock is up some 50%.
What is odd about their campaign with Panera Bread Co (PNRA) is a tool very few activists have used in some time, a la 2007, which is raising debt to buy back shares. Panera announced they will be authorizing $500 million of new debt, in which they will use to buy back $500 million worth of shares over the next 12 months. The impact of ZIRP has been up for discussion for a while, but this quote from PNRA CEO pretty much sums it up:
"The Company expects to purchase $500 million of shares within the next twelve months, through a combination of cash on hand, cash flow from operations, and $500 million of new debt, taking advantage of the attractive current interest rate environment." [emphasis added]
Here is a link to Press Release.