According to the USA Today:
ABC’s Lost is losing viewers, fast.
The island mystery Wednesday averaged 12.8 million viewers — its smallest audience yet — and was down by more than 2 million from last week’s return of the series after a three-month break.
In its new 10 p.m. ET/PT time slot, where it moved to get away from the competition of American Idol, Lost finished 2 million viewers behind CBS’ CSI: NY, though it comfortably won among the young adult audience. The depressed ratings amount to little more than half the show’s peak audience of 23.5 million at the start of its second season in September 2005, when the contents of the hatch were revealed.
Critics and fans have complained about the show’s sidetracking away from major characters, and analysts say the long hiatus may have sparked a loss of momentum. ABC next season is likely to air the show continuously from January to May, in a pattern set by Fox’s 24.