Wireless carriers’ data collection and selling practices are increasingly setting off alarm bells among privacy advocates, The Wall Street Journal reports. In particular, the Journal notes that there’s heightened anxiety about Verizon’s Precision Market Insights product that collects, stores and sells information about users’ web browsing habits, their locations and their demographic backgrounds. Verizon insists that it’s anonymizing the data it shows to third parties and is only selling data on large groups of customers broken down by geography and other demographics. The carrier also says that it has always collected this sort of data and has always been willing to hand it over to law enforcement officials if compelled by a search warrant.

All the same, the Journal’s report raises questions about just how comfortable users would be with having so much information on them sold to third parties. In particular, the Journal notes that SAP has released a new data collection service this week that “will sift through huge volumes of data about how and where people use their mobile devices and then share the revenue from selling the information with the wireless carriers providing the data.” SAP’s system will create logs whenever a mobile user visits a particular website and will store “basic information about the website the user is visiting along with the user’s location as precisely as within 30 feet and demographic data.”

From there, it will analyze the data and sell it to interested parties. What makes SAP’s service particularly troubling is that it collects data with remarkable granularity and can “provide statistics to clients about the usage habits at a particular location of groups of as few as 50 people,” the Journal says. Needless to say, privacy advocates will have even more cause for concern if carriers’ data collection practices track ever-smaller groups of people in ever-more precise locations.