I wrote yesterday about what Google’s Interest-Based Advertising will mean for web users, particularly as regards the ads people will see, the information that will be collected, and the privacy implications. But what does it mean for advertisers?

AdWords Help includes a few help questions and answers about interest-based advertising, to help advertisers get up to speed. Here’s the key info (with sources linked).

Interest-Based Advertising hasn’t launched yet; it’s in limited beta (source).

It won’t cost any more than regular AdWords (source). Presumably it will be available to everyone.

SPECULATION: Even though there’s no specific fee, I would guess that these more targeted ads would cost more, simply because advertisers should be willing to pay more to communicate with a more targeted audience. Or perhaps they’ll cost the same, but you can choose to advertise only using interest-based advertising and not using the scattershot content-targeting. I would think that interest-based ad placements would be set in a separate section (just as content ad placements are currently selected separately from search ad placements).

Back to the published facts:

Users will be identified with “anonymous user cookies” that will associate each user with “interest categories” — like “sports” or “baseball.” Ads will be shown based on these cookies (source). Personal information won’t be tracked, nor will it be made available to advertisers (source). Users can set their own interest categories through the Ads Preferences Manager, which is already available (source).

Google plans to generate interest categories much as it currently generates keywords from content, but it’s still working out the categories (source).

Advertisers can ask to join the beta (source), or they can wait until the system is finalized. You’ll be automatically enrolled if you use AdWords.