Well, consider that I am not what I would consider "rich" (this is not a complaint!) The number would have to be $2m+ for it to be "enough" in the event I couldn't provide for my family - enough to more or less guarantee that the kids are old enough to take care of themselves (15-20 years worth.) Given that it's highly unlikely that I will reach $2m+ in my lifetime, the number will never be enough ;)
Ah, I understand. I thought you were speaking in more general terms. You want security. Everyone does, and I think everyone should have it. The idea that some people aren't good enough or haven't worked hard enough to have a place to stay, food to eat, and medical treatment they need is - to me - inhumane. America is, as a nation, inhumane.
Once someone has reached financial security, money can no longer improve his/her happiness - except in short bursts. Understanding that, I can't imagine why anyone would ever need more than 50M (which is still way more than anyone would ever need). For me, it's embarrassing to live in a country where some have tens of billions while others scrape by - and some fail to do even that.
This is an extremely unhealthy perspective.