How work affects Social Security retirement benefits

How wages affect your Social Security retirement benefits is a rather odd function of the following :
1) Your full retirement age
2) Are your total wages above $14,160 (for 2009)

If you work and are full retirement age or older, you may keep all of your benefits, no matter how much you earn.

If you are younger than full retirement age, there is a limit to how much you can earn and still receive full Social Security benefits. If you are younger than full retirement age during all of 2009, Social Security will deduct $1 from your benefits for each $2 you earned above $14,160.

See : http://www.ssa.gov/pubs/10069.html