Unfortunately, the US has government backed telecommunication monopolies. E911 is a good example of how it works. In most places in the US, E911 is contracted by the counties with the local telephone monopoly. When the FCC decided that VoIP providers had to provide E911 and gave them only 120 days to invent a method for doing that and putting it into place, the telephone monopolies refused to allow the VoIP providers to connect to E911 because they weren't regulated wireline telephone companies. It took court action to call the FCC off; the court stating that the FCC could not impose a regulation that was impossible to meet and order the phone companies to allow the VoIP carriers to connect to E911. However, there are still many areas of the US where the phone companies are still refusing to allow the VoIP carries to connect to E911 services.
Wiretapping is another example. The monopolies get paid to tap phone lines - averaging about $60,000 per tap. The equipment to do this is expensive, so the government gave the money to the monopolies to implement wiretaping capability years ago. However, the FCC says that not only will they not give money to the VoIP carriers to implement wiretaps, the VoIP companies (unlike the monopolies) must do each wiretap for free or face heavy fines.
On the happy side, Congress exempted from regulation anyone providing VoIP as long as their service doesn't connect to the publicly switch telephone network, PSTN. This means that any one with control of their own DNS can setup a SIP server, sign people up to use their server and it will complete calls to anyone else using SIP. This will break the telephone monoplies once enough people have broadband and realize they don't have to pay to have telephone service (except some tiny charge to the guy with the SIP server, or he may just do it for free). I would suggest an open source SIP server project for Windows because more people would be able to operate a Windows based server and that would speed up the whole process. There is an open source project for Linux, OpenSIP, but it is too difficult for the average enthusiest to setup and operate.
How I see this happening is that there are (soft) SIP phones and SIP PBXs that can select the least cost path to complete a call. This allows the user to use the free route when it is available. As more and more calls are completed by the free routes, people will drop the paid VoIP services. The greatest impact of this will be the phone monopolies PSTN and their very restrictive, high priced VoIP services.