Excerpts:
Good news: Majority "stayed the course".
...a huge majority of those who participate in an employer’s retirement plan have stuck with their investing plans. As a recent study shows, although typical investors have lost a significant amount of money since the beginning of 2008, their losses aren't as bad as you'd think -- and having avoided panic selling, they remained poised to capture gains as stocks have recovered.

Not so good news: The conclusion that the study drew was that most plan participants simply neglect their accounts, making regular automatic contributions but rarely making significant changes to their investments.

Others words, they did not rebalanced.

Case in point: I looked at my 1999 portfolio to see what would the balance had I kept the same investments until today. My portfolio would be down about 40% after ten years (estimating the money I contributed during these last 8 years of employment). But because I have rebalanced and changed from sector funds to passive indices and added a 70% bond exposure because of my age, down about 10% from the 2007 highs.

Entire article:
http://www.fool.com/retirement/general/200...retirement.aspx

Makes a target retirement type fund more compelling.