Updated from 6:00 a.m. ESTPart of the philosophy of Stockpickr is to follow in the footsteps of smart people. This could mean a few different things. First, it could mean piggybacking great investors like Warren Buffett or George Soros. Other times it means buying what the CEOs, employees and directors of a company are buying. These are people who know the intimate details of their companies far better than you or I do. The perfect setup is when one of these company insiders or an entire board (in the case of a stock buyback) are buying shares at the same time that some smart savvy investors are as well. Each Thursday we update the Stockpickr Top 10 Insider Purchases and Buybacks portfolio, featuring the stocks of the week that had either big insider purchases or newly announced buybacks, as well as "smart money" accumulating shares. Tiffany ( TIF) makes this week's portfolio. The New York-based jewelry store just added $500 million to its buyback plan, bringing the total amount of shares authorized for repurchase to $637 million. During the last quarter of 2007, Tiffany's board bought back shares at an unusually high rate. Since Nov. 1, it has spent about $400 million repurchasing 8.9 million shares. With 127 million shares outstanding, the new buyback plan will represent 12% of the company's market cap. In the third quarter, Tiffany experienced robust sales growth as its profits more than tripled, reaching $98.9 million, or 71 cents a share. The sale of its Tokyo store helped fuel these gains, but even without the sale, Tiffany still earned 23 cents a share, surpassing the Street's expectations. On a less positive note, Tiffany's numbers during the holiday season were dismal, forcing the company to slash guidance. International same-store sales grew by a mere 5% while U.S. same-store sales dropped 2%. That made Tiffany lower its full-year guidance to a range of $2.25 to $2.28 a share; and consequentially, Tiffany shares responded with an 11% selloff. However, management is still positive about the year ahead and will continue its store expansion at a rate between 12% and 15%. Plenty of analysts, including JMP Securities, Cowen and Co., Pali Research and Bear Stearns agree that Tiffany is a good stock deserving an outperform or buy rating and that investors should capitalize on its cheapness. But price targets had to be trimmed to reflect slow, but not dead, sales. We also like to see that activist investor Nelson Peltz finds Tiffany shares attractive. He recently bought 3.6 million shares of the company, at an average price of $35.58, making him the largest holder of Tiffany with a 7.9% stake. This well-known turnaround artist, who has made billions as a corporate raider and activist, started a hedge fund, Trian, in late 2005. He also holds Cadbury Schweppes ( CSG) and Kraft ( KFT).