Ask HN: Legality of sharing personal data?

I know this is a particularly sketchy sounding title, and every response will be prefixed with "IANAL", but I was wondering if anyone had any experience with sites that share personal data.

Here's a similar idea, but not exactly what I'm looking to do (not the same target group at least):

Recruiters on average look at a lot of resumes, technically with no permission to share (though also no ban on it). Were there to be a website where users (HR folk) get "credits" for each resume they upload and/or categorize, and can use these credits to download other resumes, would this be legal? Now what if the data isn't resumes, but just names and phone numbers the recruiters pick up at networking events? Now what if the HR reps could purchase credits for money?

It sounds like something that's informally done now. It also sounds sketchy, but there's a line between "helpful to everyone" and "spammy" which I would never cross.

Obviously I would consult a lawyer if I wanted to go through with such an idea, but I wanted a quick sanity check to see if I'm way off base here.