We’ve heard that Shasta Ventures put $3.5 million into LinkedIn competitor Doostang, adding to the million or so that they raised previously in an angel round.

The service, which we first covered over two years ago, is a job site and social network where new users have to be invited by someone currently on the site. That keeps growth small, but the site has been known for having very high end jobs and job candidates.

So far, Doostang has no revenue model – everything is free. But that’s changing from what we hear. No details yet, but I’d expect users to be able to generate fees from recommending friends for jobs (an activity that is already encouraged on the site).

Currently Doostang has just over 300,000 registered members and 4,633 jobs listed. Get your invitation to Doostang from InviteShare here.