Facebook wants your address and mobile phone number

But it's not sure exactly how to ask.

It's a complicated digital courtship, particularly because Facebook doesn't just want this data for itself -- it wants to "share" this info with all of its friends, which in this case happens to be app developers (think FarmVille, Compare People and Where I've Been -- all that non-Facebook stuff that pops up in your news feed).

That may sound confusing, but the debate over this Facebook phone-number-sharing -- which caused Facebook to backtrack a bit from the request after bloggers and users expressed outrage this weekend -- essentially comes down to two related questions:

Why does Facebook want your phone number and address?

And, based on what you think about that answer, is it in your interest to hand this personal information to the network?

Let's start with the first question.

Facebook -- perhaps obviously -- doesn't want to call you to chat, or stop by your house for tea. So what's its motive for asking for these personal details?

The social network says this info helps app developers create programs and games and little social widgets that make Facebook more fun and useful.

Potential examples: A travel app could send you text messages if your flight is going to be late; a shopping app wouldn't have to ask you where to send a gift you bought -- it would just send it to your default Facebook address.

In both of these instances, the advantage is convenience. You don't have to retype your address every time you use a shopping app. This is somewhat similar to how many internet users deal with Amazon or iTunes. You save your address and even credit card number so that purchases require one click.

But Facebook is different. Sharing phone numbers and addresses with Facebook means that data potentially could go out to an unvetted list of app developers, some of whom would trick users to get information that they could sell to advertisers or spammers, said Chester Wisniewski, senior security advisor of Sophos, a security company that's been critical of Facebook on this point.

This issue of what information app developers get and how is what stirred up all the controversy this weekend. Facebook announced late Friday -- so late that a blogger at All Facebook suggested the company was trying to hide the news -- that it was making "user's address and mobile phone number accessible as part of the User Graph object."

Ahem. So, basically, the company made it possible for users to give these personal details to app developers if they chose to do so.

The uproar that followed concerned how confusing this whole process is for average Facebook users.

The blog ReadWriteWeb put it this way:

"There is very little here to call attention to the fact that Facebook would now be sharing something that it previously did not share."

Facebook acknowledged these concerns in a blog post Tuesday. The company backpedaled from its earlier statement, saying it still wants to give developers access to phone numbers and addresses, but it hasn't figured out the best way to present this information in a clear way to the public.

Facebook's Douglas Purdy phrased this in onward-to-the-future-speak:

Computer Security
"On Friday, we expanded the information you are able to share with external websites and applications to include your address and mobile number. ... Over the weekend, we got some useful feedback that we could make people more clearly aware of when they are granting access to this data.

"We agree, and we are making changes to help ensure you only share this information when you intend to do so. We'll be working to launch these updates as soon as possible, and will be temporarily disabling this feature until those changes are ready. We look forward to re-enabling this improved feature in the next few weeks."

So that was a lot of setup to get to the heart of this section:

Why does Facebook want your phone number?

Part of it is that ease-of-use stuff. But the big-picture answer is that Facebook wants to be, like Google, a personalized center of the internet -- the hub that other websites must branch off from.

The site is on its way to being just that, since lists of users' friends, preferences and, increasingly, contact info are logged on this one website.

The blog All Facebook explains further:

"By serving as a centralized identity provider, the social network makes registering for new sites as easy as a couple of clicks."

Now onto that second question:

Do you need to give this information to Facebook? Or do you want to?

Wisniewski, at Sophos, said that should be up to the individual.

But the real key, he said, is that Facebook should make it easy -- or at least possible -- for users to avoid giving up this info if they choose.

You can do that now. But you really have to know where to look.

If you don't want app developers, who could use your information to develop cool apps or could sell it to scammers, to know your address and phone number then don't give that information to Facebook in the first place.

Check your "account settings" to see whether you've already given up that information.

You also can control the information you give to app developer -- again, if you know what to look for. When you enable a new app, a "dialogue box" pops up on screen that lists the information you're about to give away.

Look carefully at that list and if you don't trust the app with that info, then don't approve it, Wisniewski said.

To see what info you've already given up to developers, go to "account," then "privacy settings" and then, at the bottom of the page, "apps and websites." You'll find a list of "apps you use." Click on "edit settings" and you get to look at that list, see what info you're giving over, to whom, and what info the app most recently accessed. Click on an individual app name and then on "show details" to see what data was most recently accessed.

For now, Wisniewski suggested erring on the side of caution:

"As far as advice goes, I certainly wouldn't share that information and don't see any reason for it to be stored anywhere but on my friends' cell phones, to be honest," he said.

Others are more comfortable with the idea of sharing info with apps.

The blog Inside Facebook writes:

"Most critics have immediately focused on how greedy developers will request the data in order to spam users, which is a valid concern. But the access will also enable the creation of apps that keep friends connected via SMS and facilitate e-commerce by pre-populating delivery details.

"Though the risks are high, Facebook should not impede innovation for fear of spammers, but instead push forward while minimizing negative outcomes by helping users make more informed decision(s)."CNN