Facebook is one on many that track users ' lives , a report says . Such ` ` social discovery '' apps seek to help you meet people -- old or new . Privacy has been a factor that slowed growth of such apps . But for the folks from Mark Zuckerberg 's company , such an app could have another payoff . Facebook also could use the reams of data to sell advertising .
Facebook is one on many that track users ' lives , a report says . Such ` ` social discovery '' apps seek to help you meet people -- old or new . Privacy has been a factor that slowed growth of such apps . Facebook also could use the reams of data to sell advertising .