The worst part is that anybody with data they really are trying to hide from CBP can circumvent this so easily and in so many ways.
TrueCrypt offers features that you can plug in an alternative password to unlock a benign phone partition with no sensitive data on it. Further you can setup a panic password that wipes the phone when you enter it.
Others suggested a more low tech approach is just mailing your phone overseas rather than carrying it with you.
That is what is so monstrous about this practice is that our rights and privacy are being taken away and with no substantial increase in security as a result.