You can cross-reference the Crunchbase API to have filters on the companies such as funding, employee coutn, location, etc. That would guarantee the startup fits the profile of what the applicant is looking for.

Great point. One way I can think of is to moderate each and every job submission. This could be costly in terms of manpower. Maybe put a requirement that your business must have 10 or less employees.

I don't think so, it's user-curated. If the job is not interesting, it won't be retweeted so it won't appear at the top of the page, just like HN

Who goes on such a site? Jobseekers. Which jobseeker has an incentive to retweet a job s/he finds interesting? Usually YOU want the job you find interesting. Why retweet it when this makes it harder for you to get the job?

Jobseekers are not expected to retweet. Company stakeholders and relevant jobseekers friends are.

And what happens when you add retweeting spambots into the mix?