Primarily driven by their familiarity with the company that they work for, many investors in 401(k) plans are loaded up on company stock. Apparently the lessons of Enron and WorldCom have been lost on a large number of investors, the Associated Press reports.

In 2004, 12.5% of investors in 401(k)s had 50% or more of their assets invested in company stock, according to the Profit Sharing/401(k) Council of America. While that's down from 20% in 1999, it's still too high an exposure due to the risk of a single stock falling in value, according to the organization.

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