Carl Icahn doesn't stop.He was one of the most hostile of the takeover kings in the 1980s, eventually taking over TWA. More recently he has started a multi-billion dollar hedge fund that often takes activist positions. His M.O. is that he usually accumulates a decent size position and then gradually becomes more and more hostile or active. Time Warner ( TWX) is a great example of his approach. Icahn began accumulating stock in the $17s, bought more as it dipped even into the $15s, then proposed a massive restructuring of the company. CEO Dick Parsons and the board didn't capitulate, but instead stuck to their plan, which was similar anyway to Icahn's plan, and the shareholders have been rewarded with Time Warner stock recently trading in the $22s and as high as the low $23s. At Stockpickr we follow Icahn's positions as he begins accumulating them and then we document what happens afterward as he goes active. Last week, Icahn filed a 13D filing on biotech company Telik ( TELK). Icahn over the years has become an expert on cancer drugs and is, in fact, the chairman of Imclone ( IMCL), another company where he started as an activist. Imclone produces the enormously success cancer drug Erbitrux. In the Telik filing he stated that he now owns 9.92% of the company, or 5.2 million shares. He also stated that he believed the shares were undervalued. A 13D is filed not only when an investor accumulates over 5% of a company but when he has the intention of having some discussions with management or other large shareholders. A passive investment is usually signaled with a 13G as opposed to a 13D.