We don't have any plans to include privacy settings for any data at this time. We built Fuelly specifically to share as much information as possible about fuel-ups and mileage, and there are lots of alternatives out there if you'd like to track your mileage privately. I completely understand the need to keep some information private, so you'll have to weigh how much info you want include with your fuel-ups. The minimum to use the system is car make/model, distance, and fuel volume—where you go from there is up to you.
I'd be curious to hear other user's thoughts on this. Every other social networking/information-sharing site has at least some controls to limit who can see certain data.
If you want people to use this site and regularly update their data, its going to be hard to convince them to do that if they have to still keep information elsewhere as well. Facebook is so successful because its a one-stop shop for everything. People don't mind putting up pictures and detailed profiles because they have the ability to restrict who views that data. If they didn't have that ability, many wouldn't add detailed info. By not letting people have more privacy/security control over data you are actually discouraging the sharing of "as much information as possible" because people will just provide less information.
One reason Fuelly is different from the sites you mention is that it's not a one-stop shop for everything. Fuelly has a very limited focus (gas mileage), and the information isn't as personal in nature as some of the Facebook stuff. Also keep in mind that we're very early in the life of Fuelly. The site has only been up for 18 days, and we're very open to ideas and what people want from the site. So maybe I was a bit too strict with my response. I should have said that we don't have plans to make anything private now, but that could change as we hear from people who want privacy controls.
We talked about it early on, but the main problem of introducing public/private data is constantly having to worry about The Wall between public and private data. So we'd have to be super careful about which things can be marked private and we'd have to make it very clear to users that maybe all their fill-ups are private but we will share their mpg with other owners of that car, or only in aggregate vs. individual. Then there's the whole question of logged-in members having visibility vs. the general public (including google scraping pages for the search engine).
It's such a complex thorny issue that we decided to avoid by just forcing everyone to be public about seemingly inconsequential data like how far you drove, how much fuel you purchases, and what it might have cost. The entire site operates on the sharing and comparing of data, so it's helpful if everything is considered public anywhere we might want to compare your MPG to other users.
I'd love to see some additional privacy settings. Granted, what we say on here my not include anyones extreme identity information (not like we'll be trading Soc Security numbers) but it's bad enough how easily we can all be tracked on the road (god bless EZ Pass) any additional privacy settings would be good as long as it doesn't take a dozen clicks to add a comment, or force you to log back in every 30 seconds.
My biggest concern is that someone sees I regularly hit the only X station in the town of Y every Z days. It certainly seems possible, however unlikely, that someone could make arrangements to have at me, my wife, or our vehicle, children, or some combination with very little planning.
I suppose I could and should stop tagging my fuelups with town/city and station name, but I'd love to be able to do some analysis of prices vs location later, say. Being able to privately tag or comment on fuelups in some way with that information wouldn't be a hugely difficult thing to implement, and I think it would add to the usability and functionality of the site/service overall.