Optimal amount to put in FSA to minimize expense

I despise programs like FSA. If the government wants to make some amount of medical or child care expenses tax deductible, then that's great. But a giant program, tied to employers, and administrated by third party agencies like Wageworks is the worst possible way to do things.

When you do it this way:

1) There are extra administrative costs

2) Participants are basically "gambling" against giant companies with pools of actuaries.

3) A lot of people miss out on the deduction because they are unemployed or self employed, or their employer simply does not offer this service.