Love folks getting all wrapped around the axle on these things. It is merely an OPINION. Time's Person of the Year (formerly Man of the Year) has always been more a news gimmick then anything else. It was originally started in 1927 to remedy the fact Time had failed to put Charles Lindbergh on the front cover following his historic flight. Time has made it abundantly clear that the purpose is to highlight an individual who has been the most influential on the world stage that year and despite the fact many very admirable people have been chosen it is not intended as either a prize or honor.
Even the concept of "person" has changed over time. It now encompasses groups (in 2011 it was "The Protester") and even objects (1982 "The Computer" and 1989 "Planet Earth").
Some choices have been questionable and some valid at the time more of an embarassment later. For example in 1931 it was Pierre Laval then Prime Minister of France. In 1945 he was executed for collaboration with the Germans during WW II.
All US Presidents have been selected except Presidents Coolidge (in office at the time of the first Man of the Year selection), Hoover and Ford. Many have been two time winners including Preidents Nxon, Reagan and George W Bush.
There has indeed been a rouges gallery as well. Adolph Hitler, Joseph Stalin (twice) Nikita Khrushchev, Ayatollah Khomeini. It is hard to argue against the criteria when once again one realizes, and Time has repeatedly stated, it is not intended as an honor but an opinion on the most influential that year. Remember even Speaker Gingrich has been selected.
While I think the selection made sense in 2008 for the President, I think (opinion) there were those, especially given the criteria change to include groups, that would have been better choices for 2012. But like the Time editorial board, that is just an opinion.