how much parenting is enough?

I"D never heard of so-called Tiger Mothers before yesterday, but I suspect we'll be hearing the phrase again when Amy Chua's book comes out next month. (For those unwilling to pay for a subscription to read her essay in the Sunday Times, there's a non-paywalled summary here).
A Chinese-born mother of two daughters, both of whom were musical prodigies, Chua's basic argument is that there is no great mystery about why research constantly shows Chinese kids outperforming not only than other ethnic minorities but often white children at school. Producing a genius, she suggests, is easy: it just means no playdates, no sleepovers, no games, no acceptance of anything other than A grades (when she came second in a history contest as a child her father told her to 'never never disgrace me like that again') and intensive coaching at piano and violin that borders on the terrifying. (She readily admits telling her own daughter that if she didn't master a piano piece all her stuffed animals would be burned, and offering her recalcitrant three year old a choice between standing shivering outside in an icy Connecticut winter or learning the piano).
Your first thought on reading it is for the children: when do they play, relax or have fun in this regime? But my second was for the mother. When on earth does she do the same?
I initially assumed, reading about how she supervised piano practice for 90 minutes minimum a day and attended every one of the music lessons personally, that she must be a stay at home mother devoting her life to the zealous pursuit of perfection. Then I realised that she's a Yale law professor, which means she was presumably finding the time for all this frenetic uber-parenting on top of working.
Not many parents do it quite like Chua (although she says this is normal in Chinese immigrant families). But on a far lesser scale, many of us parent now more intensely and competitively than we were parented ourselves: more one-on-one time, more extra-curricular activities, more coaching and tuition on top of school (because everyone else seems to be doing it), more frantic competition although it's debatable how much good it ultimately does. And I also wonder how much that contributes to the pressure working parents feel themselves to be under.
It's arguable that a heavily diluted version of Chua's regime - limiting television, say, and encouraging kids to aim high - might be beneficial. But are tiger mothers the timely rebuke to lazy Western parents one suspects she feels herself to be? Or would some of us be better lowering, rather than raising, the parenting bar?