A man walks into the bar…

That’s the start of countless jokes, but it’s not a joke for SceneTap. For the Chicago-based startup, a man walking into a bar is just another event that can be tracked and analyzed.

Thus far, SceneTap has tracked 8.5m such events at more than 400 bars and nightclubs using cameras that allow it to determine how crowded a bar is, the approximate ages of patrons and male-to-female ratios.

For SceneTap, the goal is to provide “a new look into nightlife through the eye of technology.” For venue owners, the company’s technology can provide greater insights into customers. For club-hoppers, SceneTap hopes that technology will turn it into an indispensible resource for finding the perfect spot to spend a night on the town.

Currently, SceneTap is working with venues in seven US cities. One of those cities is San Francisco, a market the company entered last week through partnerships with 25 venues.

Perhaps not surprisingly, SceneTap’s expansion is putting it on the radar — and in the center of controversy. VentureBeat’s Jolie O’Dell had harsh words for the startup, suggesting it’s no better than the now-shuttered Foursquare-based Girls Around Me app. Other commenters have referred to SceneTap as “creepy” and suggested that they’ll avoid venues using it.

According to SceneTap, all the data it collects is anonymous in nature and nothing it gathers is stored permanently. But some of the visceral reactions to SceneTap highlight an important fact: data collected passively and anonymously can still be problematic.

That data is being collected isn’t always problematic. And the nature of the data sometimes doesn’t matter. What often matters most: the manner in which it’s being collected. In the case of SceneTap, the idea that hidden cameras are silently scanning the bar keeping tabs on crowd sizes, male-to-female ratios and patron ages is, to some, bound to make a bar that was once a favorite hot spot into a not spot — even if one trusts that SceneTap isn’t doing anything that would expose personally identifiable information.

Whether SceneTap will become an ubiquitous part of the nightlife scene remains to be seen, but one should expect more and more companies like it to emerge, potentially helping to create new opportunities for business owners and marketers while at the same time creating tensions between business owners and concerned customers.

The lesson here for businesses considering technologies like this: there’s a balance between trying to gain more intelligence about customers and making dumb moves that lead your customers to question whether they should be your customers. At the end of the day, the key is making sure that in the rush to learn more about customers, businesses don’t go too far and turn them into former customers.