I don't really want your personal data, but I need an email address and password to provide a degree of security and a way to reach you for service-related issues. I'm not going to sell it, rent it, or otherwise disclose it. I am not (currently) hosting this in a secure environment, so I make no warranties as to the level of security that thugs need to go through to get past me and get at at your data, but hey, there's a reason I limit this to email/password. I do need an email to contact you about site related stuff and for things like password reminders, so chill about my asking for it. I will not spam you. Nor will anyone else as a result of your use of this site. Really. Unless someone beats me severely. And that's not an invitation to do so. And the only reason I ask for your name is so that the site can use it when addressing you.
As for the data that you put on the site (i.e., your flights, airplanes you fly, the date of your last medical, etc.): I do not share this data with anybody either without your explicit consent. For example, you can tweet your flights on twitter or post them on facebook, and you can mark any flight as "public" in which case you are explicitly making it public data. (If you tweet a flight but do not make it public, then the date and route of your flight are shared, but other details are not shared). In tracking problems on the site, however, I may need to occasionally dive into the database to make a diagnosis, and that means that I will see your data. Of course, as explained above, I dont' want (nor do I request) a lot of personal information about you, so this data cannot be tied to a person beyond your email address.
There is now a Facebook group for MyFlightbook, and MyFlightbook may include Facebook widgets on the site, and these widgets may use Facebook cookies to determine things like your status as a fan and such. If you are a member of Facebook, Facebook may be able to deduce that you use MyFlightbook. Please see the Facebook Privacy Policy for more information about their privacy policy. MyFlightbook never, however, explicitly shares any information with Facebook.
Now, there is one important exception to the above that I do need to call out. I use Google Ads on the site, and they use cookies. In fact, they are now doing "interest based" advertising, which means that they will probably figure out that this is an aviation-oriented web site, and may conclude that you are interested in aviation. Here is some slightly more legalese detailed information: