We get calls from 000-000-0000 quite often. I pick up, say hello, and if there is no immediate (within 2 seconds), I hang up.
When I am watching the grandkids, I don't pick up the phone if I don't recognize the number that comes up on the caller ID.
Heh, my habit got my DH nowhere yesterday. He called the landline of OldestDD&family (where the kids and I were) and the number that appeared on the ID was the 000-000-0000 number. So I didn't answer.
Oh well, if he wants to block his number from Caller ID, then he's taking the gamble (and losing) if he wants me to answer the phone.