I recently revisited the AdSearch idea and had these thoughts to add.

Users search for ads for products and services using related categories, names, brands, or phrases.  Results can be ranked in several ways, click-through normalized over time for example.

Ads are mostly crawled in the beginning but increasing number of ads are submitted directly by advertisers.  This means more metadata can be collected from advertisers and noise can be reduced by rating advertisers.  One of the obvious uses of rich metadata is price comparison.

Advertiser rating is also reflected on result ranking so ads submitted by a well-behaved advertiser will rank higher than abusers or recently joined advertiser.  This will create a new market for advertising service companies leveraging their rating level.

A new market can be created by connecting product reviewers with merchants.  This service works liket this:

1. Product reviewer creates a reviewer account and submits a review.
2. Appropriate merchants are notified of the review and signs up as a provider of the reviewed product.
3. The reviewer buys ads on AdSearch to attract potential buyers with their reviews.
4. When the buyer gets to the review page through ads or review panels, they will see a list of merchants carrying the reviewed product and prices they are available at.
5. Clicking on the buy button leads to either the merchant's checkout page or the AdSearch purchase service.
6. Reviewer is rewarded with either a cut of the sales or a listing fee from merchants.

Reviewers and merchants are also rated to prevent abuse.

That's it for now.  I particularly like the way reviewers become advertisers and the way more metadata can be collected over time.