There's a solution to that problem - peer to peer - as in file-sharing. Create software that sits on each persons computer. This is freely downloadable. Users input as much information as they want into it, and it reaches out and grabs other users' data like file-sharing, and filters it to any sort of criteria.

This solves the chicken and egg problem.

People can make money on this by offering hosting services. It can be a hassle for the average user to run and update the software on their computer so many might opt to pay for a cloud service.

This model can also be used for business discovery. Google and ebay can only do so much, you might want complex querying and reporting.

edit: The software solution can be as simple as publishing rdf data. The Protege ontology editor (open source) is already available. Users could simply start publishing their data profile right away, and conventions would form around what you should be putting in it. Protege also has querying facilities built in already. This was actually the semantic web vision.