Problem is with subsidized prices. When operators/carriers sell "cheap" phones, they want some return to investment. Which means blocking VoIP, Skype and IM services. Currently they make bucks with calls and SMSes. This the reason why they don´t like the loop holes in THEIR phones (as they present it). This is the reason why carriers don´t want to subsidize N900.
Another is that people don´t want to spend $500 to mobile, even it means that they have to bind themselves to fixed terms for long periods, if they want "cheaper" phones.