here), between June 2009 to June 2010, "Interconnected VoIP subscriptions had increased by 21% (from 24 million to 29 million) and retail switched access lines had decreased by 8% (from 133 million to 122 million) during the preceding year. The combined effect was an annual decrease of 4% in wireline retail local telephone service connections (from 157 million to 151 million)".
Those 6M missing connections (without considering population changes) - are probably served now by wireless voice providers or by other VoIP services (the report does not include OTT providers such as Skype but does include operators such as Vonage).
Of the 29M VoIP subscribers, 24.2M are VoIP subscriptions that were sold with a broadband internet service, and 4.6M sold as a "standalone" VoIP subscription. 3.3M are "Nomdic" - "having the capability to use the service over any broadband connection to which the customer has access, for example, at a hotel or vacation residence"