We signed our ROAs but we wont be validating anything from the ARIN region. I believe you will find this to be the norm. The tool provided by RIPE also ignores ARIN by default.
Someone will probably tell me that I am being arrogant again, but basically you are asking me to help protect your routes. And you want me to sign something first. I am not going to even read that agreement. I do not believe I am alone in this. Regards Baldur