No, I don't want to be your social-networking friend

Dear Friend (if I may still call you that),

Recently I received an email inviting me to be your friend on LinkedIn, Facebook, MySpace, Bebo, Friendster, or some other professional- or social-networking website.

I receive many such emails, which I pretend I don't get. But LinkedFaceTickleFreakSpaceFriend, or whatever you call the website, keeps sending messages claiming to be you, so I feel compelled to respond.

I'm sure you mean well, and I'm flattered. But I'm not sure you've thought this through. At the risk of sounding unfriendly, this is why I can't be your friend:

1) Your friends may not be my friends. Your friends may be hyper-aggressive salespeople, spammers, stalkers, random jerks, or just plain nuts. Not that I think your contacts are, but how do you weed out the weirdos online? As you know, I work at a well-respected university with an impressive name. It doesn't hurt my feelings that my work affiliation is probably why you want to link to me, as opposed to my killer rendition of "Hunka Hunka Burning Love." My email and voice mail already overflow with demands from would-be friends that I buy their whirligig, hire their nephew, or find a spot for their child in the next freshman class – mostly from people I've never met. If I joined you on BooBooFunnyFaceCookBook, or whatever you call it, I would never have another moment's peace.

2) You're a friend, not a revenue stream. When you send me photos, I frame them and display them in my home. When you post a photo, or anything else, on Friendster, "you automatically grant ... to Friendster an irrevocable, perpetual, nonexclusive, fully-paid, and worldwide license to use, copy, perform, display, and distribute such Content...." What a fun group! It gets better, though. On LinkedIn, you're not just a professional contact, you're "rich user profile data," all the better to sell to advertisers. Facebook encourages advertisers to "pair your targeted ad with related actions from a user's friends." So you're hanging online with friends, and some giant, hungry Facebook spider is tracking your movements and selling that information. Can it get any creepier than that?

3) Well, yes, it can. Once you give companies personal information, they can turn you into something you're not, as I learned making online purchases. Recently I signed onto eBay and was greeted with the message "John, fuel your passion for Male Nurse Action Figure!" I bought my son a toy because he's interested in medicine. Now eBay thinks I want to meet guys in surgical scrubs. Amazon.com thinks I need a subscription to "American Girl" magazine. I won't bore you with the hygienic product offers I get from retailers that have decided I'm not only female, I'm perpetually pregnant. Not only is "personal data" the newest oxymoron, it's not even personally correct.

We already know that prospective employers Google your information on sites such as MySpace. I imagine networking sites could make quite a bundle by selling you back the compromising photos you shared in a moment of insanity, or better yet, charge to remove compromising photos from your profile that aren't of you.

4) Corporations used to become billion-dollar enterprises by owning stuff: airplanes, oil tankers, rain forests, that sort of thing. AOL bought Bebo in March for $850 million because it has ... a list of your favorite 1980s bands and a photo of you doing the chicken dance at your cousin's wedding? I don't want to ruin anyone's economy, but if the whole social networking boom is built on your performance of "Being With You," then dude, it's doomed. And then what happens to your personal data? Snapped up in a fire-sale by an ISP in Uzbekistan?

5) Most important, friendships should be real, not conducted through a proxy such as MissingLinkSausageFaceSourPickle, or whatever it's called. Media hype would have you believe everyone is Facelinking, but a June 13 press release from The Conference Board puts the percentage of social networkers at 25 percent of those online. Seventy-five percent of us still like talking to real people! Alert the media! Or better yet, just give me a call. I'm always happy to hear from you.

• John Lenger, an editor and journalism instructor at Harvard University, has written about Internet privacy issues for a decade.