In close relationships, snooping on another's mobile device is commonly regarded as an invasion of privacy. The prevalence of such behavior is, however, difficult to assess. We compared two in-person survey techniques, one in which the question about snooping behavior is posed directly, and one in which strong anonymity controls are employed. Results (n=90) reveal that, while in the first case 10% of respondents admitted to snooping, in the second the estimate was 60%. This shows that, although there is a potent social desirability bias at play, strong anonymity controls do improve estimates. Furthermore, it suggests an alarming prevalence of snooping behavior among the target population.