Just how personal can advertising from the Web giants get? That’s a question you may be wondering after reading my article in Monday’s Times and the related blog post. With big Internet companies, which already have a lot of data about users, moving into the ad network business, is every ad you see on the Internet going to reflect what you have been doing and reading about lately.

To get one reading of this, I asked four Web giants - AOL, Google, Microsoft and Yahoo – a simple question: can they show you an advertisement with your name in it?

This question highlights their ability to connect personal data that presumably you volunteered when registering for e-mail or other services to advertisements. In this example, I asked them if they could fulfill a request from Procter & Gamble to run Tide ads that include the viewer’s name. (Mine might say: “Louise, Buy Tide Today.”)

This is both a technology question and a question about their self-imposed privacy policies. There are some things that companies can do, but they choose not to do. Of course, they can change that choice later. As the technology becomes more advanced along with the experience using these tools, there will be important policy issues to confront. Today, none of the four companies offer ads with user’s names in them; indeed, it would raise a red flag for them to do so. But, the four companies vary when asked if they “could” do this.

Microsoft says it could use only a person’s first name. AOL and Yahoo could use a full name but only on their sites, not the other sites on which they place ads. Google isn’t sure; it probably could, but it doesn’t know the names of most of its users.

Let’s start with AOL, which is a unit of Time Warner. AOL does have the ability to offer ads containing people’s names, which are provided to AOL during registration. But, if AOL offered “name-ads,” which it has no plans to, its privacy policy only allows it to place those ads on AOL-owned sites. The company has a policy against sharing its members’ names and e-mail addresses with any other party - even the ad networks that it owns: Advertising.com, Tacoda and Quigo. Those ad networks sell ads for AOL and for a range of Web sites using data from all of those sites to make the ads relevant. But the amount of data the ad networks have to work with is the same for AOL as it is for their other customers.

Yahoo is open to the idea of name-ads. A spokeswoman said that Yahoo can customize ads with people’s registration information, if they are logged in. This is similar to what Yahoo already does on its site for some of its own products, like e-mail. If I had an e-mail account with Yahoo, I’d be greeted by “Hi Louise” when logged in. But, the spokeswoman noted, Yahoo does not pass information like names to advertisers. The registration information is simply used by Yahoo for ads. Yahoo has a new product called Smart Ads that moves very close to this sort of micro-targeting by using data about its users to give them very specific offers for stores near them.

Like AOL, Yahoo does not use its registration data to the benefit of companies - like eBay and Comcast - in its ad network or in the Blue Lithium network that it owns. Yahoo does use some of those external sites’ own data to help target the ads on their sites.

Microsoft stands alone on the name-ad question. The technology company has gone beyond policy making and created a technological barrier to using people’s personal information in advertising. The company uses an algorithm to pull demographic information from user’s registration (gender, age, ZIP code) and then places that with their behavioral data about what sites they visit. Once the algorithm has been applied, Microsoft says it has no ability to trace the data back to an individual consumer. You can a white paper here about how Microsoft keeps ad-serving separate from user’s personal information.

But there is a catch. Microsoft does not consider first names or nicknames to be personal information. So, they could run name-ads with only people’s first names.

Google told me that they “might” have the technology be able to serve such ads that show your Google user name, and that they have no current privacy rule against it. Google is different from the other three companies in that it does not use either behavioral or demographic data to serve ads. In fact, the company says it does not ask users for it during registration. Google also only serves ads based on the information on the Web page you are looking at—and sometimes the immediately previous page you viewed– - instead of past information about what sites you visited or what terms you typed into search For a long time Google limited the amount of personal information it collected. But as it expands, it creates many perfectly legitimate ways to ask you about yourself. You put your name into Gmail. You note your home address in Google Maps. You verify your name and address, and store credit card information too, when you buy something through Google Checkout.

For Google and the rest of these companies, the question remains how much they can, will and should use the information they gather from their Web sites to target ads in their ever expanding advertising networks?