The traditional big four, AT&T, Verizon, Sprint, and T-Mobile have all agreed to a voluntary industry standard that will see these telcos send alerts to subscribers who are about to venture into international roaming zones or go beyond what they originally bargained for with their voice, text or data plans. This is definitely a good thing, as the onus is now on the subscriber to make sure he/she is aware of what’s going on, and there is no longer any need to dispute high bills after that.
It will take anything from a year to a year and a half for such a system to roll out on an official basis, which is still better than nothing. Till then, make sure you don’t over-talk!