[tkems]

I would say that money is the root of the problem. I think that most VOIP providers don't want to loose out on unencrypted traffic (both legitimate and spam).

Also, why do I seem to always get spam from a few providers? And why aren't we holding them accountable?

[gregmac]

Money is always the problem. In the carrier world, the party accepting ("terminating") the call gets paid by the party originating it. This is why there are VoIP services that will give you a free inbound-only number and why others only charge for outbound calls.

If you're a carrier, it pays to terminate all calls -- spam or not -- by delivering them to your actual customer. You get paid by the originating carrier, and in a lot of cases you also get to charge your customer per-minute fees (or use up their prepaid minutes).

[Macha]

> This is why there are VoIP services that will give you a free inbound-only number and why others only charge for outbound calls.

This is the norm for standard carriers in Europe too.