4. Kinder Morgan ( KMI) Like HCA, Kinder Morgan has had multiple stints as a private and public company, with its most recent buyout occurring in a 2006 management-led buyout valued at $22 billion that included a consortium of private equity investors. On Feb. 11, 2011, Kinder Morgan returned to public markets in a $2.86 billion initial public offering of 95 million shares, according to Bloomberg data Since its February initial public offering, Kinder Morgan has been the most aggressive player in the pipeline space, cutting a $21.1 billion deal for competitor El Paso ( EP) that will help to make the company the largest transporter of gas in the U.S. Earlier in 2012, Kinder Morgan sold El Paso's oil and gas exploration unit to Apollo Global Management for over $7 billion, in one of the biggest post-crisis private equity investments. However, the merger faced scrutiny on potential conflicts of interest. Still, Kinder Morgan's ascendance into a pipeline powerhouse has been rewarded by a 20% stock gain since the company's IPO. On Tuesday Bank of America Merrill Lynch analyst Gabriel Moreen downgraded the Kinder Morgan shares to "underperform," while lifting his price target to $33 a share, 10% below Tuesday trading prices, on the company's growth prospects and a big overhang of private equity shareholdings. "We see the $12bn in private equity ownership in Kinder Morgan as an overhang," noted Moreen in his report. Overall, Kinder Morgan is expected to earn $9.2 billion in 2012 revenue and $885 million in profit, according to analysts polled by Bloomberg who give shares an average price target of $35.50 -- below Tuesday's close of $36.75. Six analysts rate Kinder Morgan shares a "buy," while five rate the company a "hold" and two rate shares a "sell." Company Chairman and Chief Executive Richard Kinder retains a 33.67% stake in Kinder Morgan after its IPO, or 238 million shares. Kinder and a consortium of private equity investors that includes Goldman Sachs ( GS) and The Carlyle Group, among others, owns over 80% of the company's outstanding shares according to Bloomberg data.