Objectives <p>The tendency of businesses and residents to gravitate toward safer streets complicates efforts to assess the influence of informal surveillance (or <i>eyes on the street</i>) as a crime deterrent, as it is often intertwined with other factors such as target availability and neighborhood dynamics. We leverage a quasi-experimental setting of itinerant street markets to assess the impact of concentrated retail activity on property crime.</p> Methods <p>We combine official records with user-generated traffic data from Waze (available via Waze Discuss) to identify street market locations in Montevideo, Uruguay, and link them to over 15 years of georeferenced police reports. Using an imputation difference-in-differences design, we exploit temporal and spatial variation in street markets to estimate the causal effect of retail-driven activity on thefts and robberies.</p> Results <p>Our findings show that while street markets lead to a significant increase in the number of reported thefts, they have no measurable impact on robberies—a crime type that involves the use or threat of violence. The documented effects are concentrated in small geographic units with no substantial spillover into adjacent areas, indicating no crime risk diffusion. These effects are also more pronounced in larger markets, suggesting a mechanism tied to the absence of <i>familiar strangers</i>. Moreover, the effects on thefts are stronger in neighborhoods with shared socioeconomic vulnerabilities, offering insights for geographic profiling.</p> Conclusions <p>Overall, our results underscore the interplay between urban mobility patterns and crime, pointing to the need for balanced urban policies that integrate formal surveillance with community-driven strategies.</p>