**Editor's Note: Click here for a recap of some of the most egregious bill shock moments of all time.**
They're called "silent roamers" and they present a $1.2 billion revenue opportunity for the mobile industry. While that might seem like a big number, Syniverse – which provides technology and business services for the telecommunications industry – says that's what its research shows.
The company, which works with more than 900 mobile operators in 160 countries, says a lot of global travelers still fear using their cellphones out of fear of bill shock. These so-called "silent roamers" are worried about returning home to find a big bill for using mobile services outside of their home country.
As the graphic below shows, nearly half of the 75 million mobile users who travel abroad each month, half don't use voice services and a whopping 70 percent wouldn't even consider using their phone to go online. That leaves $1.2 billion in potential revenue just sitting on the table.
(Click image below for larger version.)