I had pretty much given up on parking, when 2 weeks ago I get an email from Jennifer at parked.com telling me I have been preapproved for a parked account & would I consider parking some names with them. I have heard good things about them so I pushed about 40 names. Like jarrall said, the minimum is 10 domains.
I think you'll find that Donny (he's not the owner btw) is pretty direct: unless your names are good, you don't get in. So, all you have to do is find out by applying.