According to an item on PCWorld:
Increasing competition from Internet phone providers like Vonage and from services such as Skype is causing traditional telephone carriers around the world to look at methods to slow or stop IP-based calls that cross their networks. The key technology, from a firm called Narus, can detect VoIP packets and either block them or deprioritize them to reduce call quality. A number of foreign telephone carriers have already enlisted the company’s services.
Narus bills their product as CALEA compliant. So carrier may end up installing it in order to comply with lawful intercept requirements and would then have the functionality to cripple third party VOIP applications.
According to Narus’ website, the product has already been deployed by a number of carriers including T-Mobile.