What do the child benefit cuts really mean?

It appears that child benefit will continue to be paid to all women but from 2013 it will be clawed back through the tax system where one of the parents in the household has taxable income in excess of the 40% threshold (currently £43,875). This method is being proposed so as to avoid a costly means testing system before child benefit is paid out. Fine if both parents earn less than the threshold. But otherwise this new measure is going to undermine the principle of independent taxation which has formed the basis of our tax system since 1990. From 2013 it appears many men are going to have to pay tax on money they themselves have not received and this could be a swinging amount of tax if, say, there were three children and the man was still a 40% tax payer but earning less than £50k.