While people are busy discussing Facebook's privacy policies about user data, it's the less-direct privacy issues that constantly nag at me. I haven't seen these discussed before, although I'm sure I'm not the only one to notice them.The first issue is quite serious, regarding the information Facebook collects about us when we are not even necessarily registered members of the site, and what it does with it. Users are able to, and encouraged to, find their friends using the very helpful import function. You can upload your address book, your IM contact list, and even your LinkedIn contacts. Then, by your choice, Facebook will invite these folks to be your friends.

But what happens with this data once the action is done? Facebook keeps it around and makes decent use of it. For example, if friends who previously were not on Facebook create new accounts, then it may recommend you connect with them. However, Facebook also recommends to these people to connect with you.

That means folks who have never even been on Facebook and uploaded no information about themselves suddenly see Facebook recommending they add people they know. This is indeed useful and, for some, friendly -- but to me, this is scary.

The Big Brother feeling is very difficult to shake -- not to mention that you, the original uploader, never indicated you are interested in being these people's friend so that such recommendations drawn from your data should never have reached them.

These issues, however, are secondary and are mentioned mainly to point out the fact that Facebook does keep and make use of this data.

By collecting and cross-referencing address book data along with potentially other data sources, Facebook is potentially able to map our networks of friends, co-workers, and others -- all without us ever opening an account. Because we never provided Facebook with this information, they have no obligation toward us as to how they can use or sell it.

Adding to that, by using the data available on what networks of people, groups, and interests your friends belong to, Facebook (and those it might sell this data to) can potentially create a full profile of your interests and activities without you ever making a move.

When I joined Facebook, I recognized that while I'd like the social network to honor my privacy, when I put something online it is as good as public -- and I act by that rule. I don't let Facebook off the hook about how it should protect my data, but I treat what I want private as secret and never upload it to begin with (however precious little that might be in this connected world).

Even without the policy oversight described above, the very capability of such data collection with no obligation scares me. I understand this is how things work if an investigator takes an interest in me, but my vulnerability to data collection by actions of my friends -- without me ever lifting a finger -- is as disturbing as it is unavoidable.

This is one of the cases where I can look to Facebook for a privacy policy and security assurances, even as I recognize that, indeed, online life is public life.

A second indirect privacy oversight, which may be considered serious by some, but is still quite nagging, is the public groups, events, and other miscellaneous choices in Facebook activities.

Even if I choose to keep my profile and all of my data strictly available only to my friends and not allow them to provide it to applications they use, there's a problem: Even if I go as far as to remove any application I can from my profile, public groups are beyond my control.

So if I join a group and it's available for search in Google, for instance, then my name will appear in its membership. Prima facia, I can't complain as I did join the group of my own free will. However, it is not as simple as that.

There is an implicit understanding that if I refuse for my profile to appear on Google, it won't. Then I discover that groups I joined as a joke are indexed by Google when searching for my name.

I would advise you consider that the group owners can change the group privacy settings without a user knowing about it unless you actively check. Thus I have no control over it, and I can't trust where the information on which groups I am a member of goes.

Facebook may not be doing this on purpose, but rather by bad trust design between different components. Then again, I can't really complain -- I did take it as an underlying premise that if I put any information online, it is as good as public. That, however, does not mean Facebook shouldn't do their best to protect my privacy -- especially when there is currently an option provided by Facebook to hide group affiliations, etc., in Facebook's privacy settings.

This circumvention is a security vulnerability of the privacy compromising kind and should be treated accordingly.

Facebook's third behavior that nags me to no end is not as serious as the ones above. As of a few months ago, if I try and add a new friend and he or she, in turn, did not accept me, I can still follow the person's updates (which they allow non-friends to see).

First, I did not ask for this "follow" option, and I'd really like to know how to remove people from my "follow" list. Second, while I could visit profiles of people I am interested in at any time to see what they do, I can now more easily follow their activities, determine when they are online, etc., by watching my constantly updating News Feed... Like I have nothing better to do without this added noise.

Under normal circumstances, a stalker would have to actively enter the profile page of those he or she would want information about. This way, it is served to them and, as a secondary argument, Facebook can't track their activity as odd (stalker-like) in cases where it would need to.

Facebook does not provide an option to prevent people from following me, nor does it let me (as far as I have seen) retract my friend requests or de facto follow action, which I never asked for.

I am a happy user of Facebook, and I have often been its strong supporter on security issues, defending it when others would not. I now call on Facebook to acknowledge these issues and share with us, its community of users, what it is going to do about them.

Follow Gadi Evron on Twitter: http://twitter.com/gadievron.

Gadi Evron is an independent security strategist based in Israel. Special to Dark Reading.