Screen capture of a Google search for Fitbit profiles containing sexual activity.
Don't bother Googling for
"sexual activity" site:fitbit.com anymore. Earlier today, using those search terms would've given you the profiles of Fitbit users who were both sharing their activity logs and counting sexual activity as part of their calorie-burning efforts. As of this writing, Google seems to have acted in the interests of privacy by not returning any results for those terms. (Bing, on the other hand, returns ten results as I write this.)
A Fitbit device.
The problem comes from a design decision that probably made sense in the abstract, back when they were designing the software. Fitbit lets you set the privacy levels of various section of your online profile individually. Fitness goals are one section, activities are another. Many people are a bit self-conscious about their weight and naturally set their fitness goals to "private".
At the same time, many people want to announce to the world that they're working out. Since that's not the sort of thing most people are embarrassed about -- in fact, it's something some people like to brag about how often they go to the gym -- it's not too surprising that they set their activity log to "public".
Finally, there's the ability to manually enter activity data. Most people won't wear the Fitbit all the time, but want to count every calorie burned. Manually entering activity data lets you count those activities when you're Fitbit-free towards your calorie burn. Among those activities is sex, which burns far fewer calories than you'd think.
Combine all these factors and you have situations where your user profile hides your target weight, but shows all those intimate encounters that you faithfully logged -- not out of braggadocio but the simple desire to count every last calorie expended. The saving grace is that since Fitbit is a health program, most people's descriptions of their sexual activity in their Fitbit logs sound rather clinical. Most of the descriptions are more along the lines of "light kissing" and "vigorous activity" rather than "OMG PILEDRIVER" and "What what in the butt".
A (slightly doctored) Fitbit activity profile.
For software developers and designers, this is an object lesson in unintended consequences and privacy. The fact that Fitbit gave users control over the privacy settings of various parts of their profile shows that they were designing with their users' privacy in mind; it's just that the implementation didn't account for the fact that some activities may be private. I wonder how they're going to redesign around that problem.
For users, the lesson is that you should check your online profiles regularly. Just as you look in the mirror before you leave the house (well, some people do), you should make sure that you're presenting yourself to the online world in the way you want.