I am a huge believer in vaccinations in general and there is one major reason that has not been discussed here so far: to stop the spread of the virus to others. I believe that the benefit to society as a whole outweighs individual discomfort.
For example, cjemommy posted that her youngest couldn't get the shot vaccine because of an egg allergy. If it were me, I would then vaccinate everyone else in the family to "protect" the youngest.
For the flu vaccine, it may not be quite so important because deaths due to flu in the normal, healthy population is quite rare. However, for more serious diseases, it might be essential. One demonstration of this was a report I read recently that half of all deaths last year for measles were traced back to one, unvaccinated teen-ager who traveled abroad, returned and then infected a group of unvaccinated friends. You may think that you don't need to vaccinate because your family won't be in situations that expose them, but the fact is that it only takes one contagious (not necessarily sick) person - you wouldn't even have to know them if they used a water fountain, or sneezed on a door handle of a public restroom, or a thousand other scenarios. If the girl traveling abroad had been vaccinated, it could have stopped the progression of transmission in its tracks!
Ok, now I'll get down off my soap box!!

n my soapbox:
And, for those of you who are adamantly against vaccinations for your own children, I do know that vaccines are far from perfect and there certainly are risks that each family must evaluate for themselves. I am thankful to live in a society where we can discuss and debate these issues and have the luxury to have choices.