Steve Moore is correct that Private Foundations can become abusive the play toy of the very very wealthy with tax benefits. However, let us not confuse the parasites with the host.
The public charities' abuses and philandering gave rise to the increasing use of private foundations. The abuses and lack of results of the public charities in effect created the private foundation surge. Look at certain charitable public foundations which have become in time the exact opposite of what was intended by the founders - whether one agrees with the originators' politics or not proving Guirjieff's Law of Seven 'that which was intended, in time, becomes its exact opposite.'
If anything many - too many of these public charities and their executive directors are better known for 'giving good lunch' than accomplishing anything.
So to get rid of these 'give good lunch' executive directors, minimize abuse of the private foundation backlash to the ineffective public charities, and minimize the probability of becoming the opposite of what was originally intended let alone the harboring of worthless heir force lucky sperm club progeny - how about the biblical Joseph solution?
The private foundation would have a a life of seven fatted years. At the end of seven years it's fate is emaciation. The private foundation must dispense of all the remaining assets to other charities (but not to any other charity private or public directly or indirectly controlled by the dismantled foundation, heirs, relatives etc etc. This would be akin to rules that are negative toward interlocking directorates and brother sister corporations and subject to huge non deductible fines.)
Yes, in 7 years living or deceased - there can be abuse - but let us not defeat the better for the perfect. Besides even on the 7th day God rested so on the 7th year the private foundation can be put to rest.
Final note, it is also suggested - so a war chest is not accumulated by the giving good lunch executive director to bring to another foundation upon dissolution - 15% of capital minimum and all dividends, interest and realized capital gains be distributed annually.