Why are people so disturbed by the occasionally remarkable relevance of Gmail’s ads? It seems the better Google (and advertisers) get at matching key phrases to context ads, the more it makes some folks think something scary is going on.

I saw this on a mailing list recently (paraphrased to protect the worried):

I like gmail too, but lately they’re starting to scare me lately. The amount of information they collect and how they use it is startling.

I e-mailed a friend talking about some symptoms of a medical condition, and Gmail served up a sponsored ad offering a diagnosis and selling a solution for the condition.

So this puzzles me a little.

First, GMail has done this since day 1. And people have been worried about this since before it launched.

But why is this so troubling to people? This recent email was just one example; I read lots of people who seem bothered by this. It’s often occasioned by an ad that seemed to “know” about a recent email conversation the user had.

I don’t know what nefarious things Google may be doing with my Gmail behind my back; I can’t say that they’re not doing something wrong.

But all they’re doing with the ads is keyword-matching, just like they do with Adsense on a web page.

Companies “bid” on words and phrases, and when those show up in a context where Google serves ads, by some magic algorithm (Google for “how does adsense select ads”) Google serves up matching ads from its pool of bidders.

If an ad appears on your Gmail page, it’s not because Google is matching your *identity* and then notifying some other company that “Hey, Ryan was talking to Joe about spontaneously erupting super-vision-itis” so they can jump in and prepare an ad for you personally, cackling maniacally. It’s because the magic matching key-phrase is somewhere in that web page, and that ad was automatically chosen from the pool of available ones that matched *some* text in your current page.

Keep in mind that the page loaded by Gmail is huge; there’s a lot more text transferred to your browser than what you see on your screen at any given moment.

Gmail pre-fetches a lot of stuff to make the Javascript-based navigation smoother and faster. So just because you don’t see anything about that message you just sent on your screen doesn’t mean
that message is not in the window.

Now, for all I know, Google may be wiretapping our cell phones and selling the content to the North Koreans to kill puppies with. But highly relevant contextual ads on Gmail don’t seem to me very strong evidence of anything alarming.

Or maybe I’m just insufficiently paranoid.