An Analysys Mason study of roughly 1,000 smartphone users in Europe and the U.S. found that about 4 percent of respondents use mobile VoIP more than traditional voice services.
The study indicates that IP communications provided by the likes of Skype and Vonage is no longer just an alternative to fixed-line phone service.
Of the smartphone users who are using VoIP apps, 20 percent used the Internet Protocol-based technology more than traditional voice, according to Analysys Mason.
"As more people use VoIP as their primary voice service, then ever larger numbers of individual users' key contacts will be contactable through VoIP apps," Analysys Mason said. "The danger for mobile operators is that they become relegated to providing secondary voice services, picking up the 30 percent or 40 percent of call traffic generated by users when contacting people who are outside their core calling circle. If this occurs on a widespread basis, their role becomes marginalized."
Skype, now owned by Microsoft Corp., ranked as the most popular VoIP provider, with 79 percent of VoIP users, or 16 percent of the total smartphone respondents, relying on the company.
Use of Skype on Android-powered phones and iPhones has skyrocketed. Skype for Android devices has been downloaded more than 70 million times on Google Play, according to Chaim Haas, a spokesperson for Skype.
Earlier this year, Haas said, Skype ranked No. 4 on Apple's list of the 25 most downloaded iOS applications for the iPad and iPhone. In September 2011, Skype revealed that its iPhone app had been downloaded nearly 60 million times to date and that it had been downloaded more than one million times in the first 36 hours following its debut in March 2009.
Skype CEO Tony Bates noted this summer that "the importance of mobile and Skype's commitment to cross-platform accessibility is paramount."
"While most of the current Skype user activity is on PCs, iPhone is our top platform for downloads, and Android is our fastest-growing platform," he said.
Skype isn't the only company with a stake in the mobile VoIP market. Vonage, the Internet-based consumer phone provider, revealed Aug. 1 that more than 560,000 customers have signed up for a service that is primarily used for mobile and international calling capabilities.