The "8" refers to the Fidelity guideline of saving 8x final annual pay.
A few tidbits: Fidelity model (mentioned above) assumed 6% savings at age 25, increasing to 12% after 6 years and holding there until age 67. This also assumed that savings grew at 5.5% per year (3.2% after inflation). It also assume you need to replace 85% of your final pay.
Boston College study - for folks making 150-200K, the magic number is 10.3. Assumes 4.5% real return on savings.
A few good points are made in the article about the many factors that affect the magic number and that are unique for each person (is house paid for?, health, college, pension plans, etc.)
re: Yes, another retirement thread - RE: How much you need to retire (Posted on 10/23/12 at 2:08 pm to K E V 8 4)
thanks for the bump. this article made more sense in that it at least stated that you will need less than 85% of final pay if 1) you have no mortgage and 2) you have sent kids to college. that 2 factors could reduce your needs by a large amount.