Benefit formula changes
You can lose retirement income in a defined-benefit pension without even realizing it when your employer tinkers with the benefit formula. Among the tricks:
The "compensation" part of the equation is changed from the final year (usually the highest-paying) to an average of the last three to five years or to a career average.
The percentage benefit multiplier is cut from, say, 1.9 percent for each year of service to 1.5 percent.
"Compensation" is sliced into two parts: the amount of salary up to the Social Security Wage Base (the maximum salary on which Social Security taxes are levied, $106,800 in 2009) and any salary amounts above that level. Then a lower benefit multiplier is applied to the larger segment of your salary.
PBGC benefit limits
If your employer has not sufficiently funded its pension plan, it could be terminated and taken over by the Pension Benefit Guaranty Corp. That was the case with Bethlehem Steel, United Airlines, and US Airways, which walked away from a total of $13.8 billion in pension liabilities to nearly 280,000 vested participants in 2003 and 2005.
In most cases, you will get the full vested benefit owed to you up to the time the pension plan is terminated. If you earn a high salary, however, you could lose benefits you accrued that exceed the PBGC guarantee limit, which ranges from $12,150 to $54,000 for plans terminated in 2009. How much you'll get depends on your age (45 to 65) and whether you take a straight life annuity or joint annuity with 50 percent survivor benefit.
http://www.consumerreports.org/cro/money/retirement-planning/is-your-pension-secure/overview/is-your-pension-secure-ov.htm