[ajmurmann]

My guess is that it's a motivation problem. With email there was a huge motivation for email providers to fix spam. Email providers don't make money based on the quantity of emails sent and it's a well functioning market. The cost of moving your inbox to another provider is pretty low and there are many competitors. Contrast to this problem: telcos make more money if more calls get placed; there aren't many alternatives; barrier of entry to the market is very high; switching provider is painful; you cannot just try a different telco like you could for email.