It's always a good thing to practice safe computing, no one wants their personal data stolen. Techlicious' Elmer Montejo's article "These Popular Apps Are Secretly Sharing Personal Data" references a study by a team of security researches. He writes: "In their analysis of 55 free and popular Android apps and 55 iOS apps, the report found that a “significant proportion” of the apps shared users’ emails, names and GPS locations to Google, Apple and third-party services." You can read his article here.