All half-competent carriers require some sort of authentication before they'll allow you to spoof a number - basically prove that it is actually your number. The issue is that there isn't any practical way to prevent a dishonest or careless carrier from allowing it as there's no practical way to validate where the call can come from - and in the general case it would need to be a list, not just a single source.
Presentation numbers have a lot of valid uses - for example, arranging that calls made from various offices of a business "come from" a number recognisably as that business regardless of which office originated it.
As I wrote a few posts up, there could be ways to make it in the interests of carriers to be more selective who they'll deal with - but it'll never happen.
As it is, with a previous work hat on, I did have a requirement to set up a presentation number for one of our clients. I was looking at the documentation for the VoIP service - and realised that I didn't need to send anything in, they took our work for it as the reseller that we'd checked that the customer actually owned the number. This was for a legitimate purpose - but the scope for abusing that would be huge.
Biting the hand that feeds IT
