Eyebrows were raised when Seattle-based Jobster shredded their business model and moved to free job listings in February. It was a direct assault on Monster, which charges up to $475 per job listing. Many of the commenters in the post discussing the change said it was the last ditch effort of a troubled company.

This week Jobster quietly rolled out phase two of the plan, adding pay-per-applicant job listings to the mix. The listings are still free, but companies who agree to pay a per applicant fee are shown on the top of search.

CEO Jason Goldberg says it will be a much more efficient model than anything that exists today. Companies don’t pay anything unless they receive a qualified job applicant. This gives Jobster the incentive to make sure lots of potential employees see their listing.

During a beta period, Jobster is charging $5 per applicant. Later they’ll allow companies to set qualifications, so they will only pay for, say, the application of someone who lives in San Francisco with Ruby on Rails development skills. At that time, they will also be moving to an auction model and let companies compete for those top places on search results pages.

Jobster is also the exclusive Job Listing provider to Facebook (mentioned at the end of this post), although the new Facebook developer platform would also allow other services to add their application. The new job listings will eventually make their way to Facebook, Goldberg says, increasing Jobster’s reach exponentially.