Whenever I see someone walking around with a Fitbit, I kind of roll my eyes. Mostly because I find it ridiculous that most people gather a bunch of data like they think actually collecting the data is going to help them in their everyday lives. It's like I know that double cheeseburgers with fried eggs on them are terrible for you, but it doesn't stop me from wanting to eat them every chance that I get. Just like Steve from accounting knowing how many steps he's walked the other day is going to transform him into some elite-level athlete.
But I understand that that's just the hater part of myself talking - I'm sure there are plenty of people who use the data their Fitbits give them to help them make healthier choices on a daily basis and adjust their workouts and eating habits accordingly.
Plus, at the end of the day, they double as casual watches with great battery life, can be worn in pretty much any situation, and do all sorts of neat stuff like track your sleeping habits and monitor your heart rate.