What is a friend? I have a simple, modern definition. A friend is someone to whose home I have been for a social reason, or, if invited, would accept such an invitation. A friend is someone I would invite over to my house, too. A friend is someone I call up or send email to without a particular agenda in mind.

I have found it easy to conflate friend, acquaintance, and colleague into "friend" over the years, partly because I'm gregarious. (Although, being gregarious apparently isn't required. My friend and colleague Joe Kissell says that he finds himself in agreement with most everything in this article despite being a self-described introvert; for his view on what that means, see "Instant Messaging for Introverts," 4 April 2008.)

For instance, our TidBITS and Take Control head honchos, Adam and Tonya Engst, are both close colleagues and dear friends. When they lived nearby, we saw each other every so often, though less frequently than we would have had we not been separated by snarled Seattle traffic. Now a continent apart, we talk even more regularly, mostly about work, but with a lot of personal stuff thrown in. You know, I like them.

On the other hand, there are some people with whom I have worked for years who remain colleagues, but it would be a stretch to call them friends. I would never tell them to their faces that they remain at arm's-length, and it's rare that there's any tension. It's just a lack of being simpatico - an association of feelings and rapport that allows easy communication.

These ruminations about friendship come up every time I'm asked to "friend," "buddy," or partner up with someone in a social network. The fundamental problem with social networks is that they either encourage too much forced intimacy or put one in the position of rejecting genuine friendship.

I have found in my brief forty-two years on the planet that everyone has a different spectrum of friendship. Some people I barely know appear to consider me a friend, and that's typically charming (if perhaps misguided). Other people I have known for many years are still rather formal with me, despite hundreds of contacts.

I generally like most people I meet, and generally can strike up a conversation with any given person. But that doesn't make that person my friend (although it might me make me his or her friend). This all makes requiring an explicit choice - instead of using implicit social signals - rather frustrating and stressful.

David Weinberger, author of several interesting books about Internet culture and information (his most recent is "Everything Is Miscellaneous"), spoke well to this point at the 2003 O'Reilly Emerging Technology Conference. (His talk is available as a Web page.)

Weinberger is often ahead of his time, and he was speaking about the coming tsunami of social networking. Although I heard him say this seven years ago, it has stuck with me as an apt summary of the problem. He was talking about Friendster, the dominant 2003 social network, when someone named Halley asked him to be a friend:

I have no problem saying, yes, I am Halley's friend. But there are lots and lots of people who might ask me to be their friend for which the situation is much dicier. There are people who are acquaintances, or relatives, or former college housemates I've been trying to avoid for years. There are people for whom I'll press the Accept button not because they're friends exactly but because they're not enough not friends that I want to reject them, or because I want to impress them, or because I want to kiss their butt in public, etc. Friendster asks me to be binary about one of the least binary relationships around.

The binary problem is that someone asking you if you are a friend or not becomes a referendum on the entire relationship you have with that person. If you say No, you're rejecting an offer of kindness; if you say Yes, but mean No, you've set up a new and potentially damaging dynamic; if you ignore the request entirely, the person may notice the lack of response and be hurt.

The social networking services can't simply set up a spectrum of intimacy, either. LinkedIn tries this by asking you how you know someone (did you work together, go to school together, and so on), thus establishing a venue for a connection, since LinkedIn is a business networking site.

But could Facebook ask you to select among acquaintance, friend of a friend, person you once dated, enemy, friend, lover, BFF, drifted apart from, longing to be back together with, and who the heck is that? Pick the wrong choice, and that friend (lover, colleague, nuisance) may be dead to you forever, or may become the new best friend you didn't want.

Of all the social networking services out there, I like the approaches of Flickr and Twitter best. In Flickr, you have contacts, and you can set a contact to be a friend or part of your family. (I have friends I consider family and mark them as family, too.) But Flickr doesn't force you to ask or answer the question.

Twitter's follower/following model doesn't imply much about the relationship, although one could easily argue that the asymmetry of popular people following few and being followed by many is a kind of emergent hierarchy of importance. But at least I don't have to pretend to be Ashton Kucher's friend, nor vice versa. (Early in its history, Twitter had the concept of "friends" as well, and gave it up as being confusing.) Adam Engst also likes Twitter because of how it doesn't overload relationships; see his companion article "Pondering Friendship Online: Expand Asymmetrically" (28 May 2010).

As it stands, I've made some real friends and strengthened many existing acquaintanceships through Twitter, a rare occurrence in my previous 20-plus years on the Internet.

When I killed my Facebook account a few months ago, I had hundreds of friends. I deleted the account because of my disgust over how Facebook was handling privacy, disgust triggered epiphenomenonally by the Google Buzz debacle (see "What's the Google Buzz? Tell Me What's A-Happening," 14 February 2010).

But deleting my Facebook account was also prompted by a growing discomfort at how much of the intimate details of people's lives I was being shown outside the circle of people with whom I have that actual degree of intimacy. It had become almost like The Sims for me, with Facebook showing information about friends of friends, and constantly suggesting new people I might add to my network who I didn't know well or, increasingly, at all.

I had long joked that Facebook was Second Life for your real life, and I already had a real life that was taking up pretty much all of my time.

Facebook and other services could short circuit this problem by letting each user have social circles into which connections could be optionally placed, but which would be known only to the user, not to any friends. Keeping friend details private for you and implicit for others would preserve some of the social compact. (Facebook has a feature called Lists that offers a clunky version of this, but most of my friends still using Facebook are unaware of it.)

But social networks require massive numbers of explicit connections to drive their growth: Facebook would prefer everyone friend hundreds of people, and recommend hundreds more.

My life, however, doesn't favor quantity and growth over quality and intimacy. When we were little and another child asked, "Will you be my friend?" the answer wasn't always Yes, but it probably should have been. In my 40s, and in today's Internet, the answer, I'm afraid, is, "I don't think that's the right question."