I understand your point about the phone screen, but found that this is a trade-off. The phone screen was very ineffective for us in letting people know who we are, our size, our location, what we do on a daily basis. The open house format lets the prospective employees see us as we are, where we are. Inevitably, people drop out of the process, and it's fine with us, as it opens up slots for those who like what they see. In an open house format, the candidates ask questions as a group, which means that any particular person benefits from the questions that others ask. They see our existing staff and can decide if this is a group they want to work with.
We are upfront with the candidates that we can't hire all of them, and therefore it seems like a fair exchange to do something for the "unchosen" as a bonus for coming in. Brooke and Noah have helped by providing guidance for them, and we have all tried to create a community of the unchosen.
The core concept being promoted here is that the current recruitment system is broken, and it is the fault of all of us who unquestioningly perpetuate it. My response is to experiment with different ideas until we find a model that works for all parties involved. I don't have a magic wand to provide the solution, but do keep notes on what hypothesis is being tested, what seems to work, what doesn't work and what possible improvements we should try.
I admit that I tend to think of things initially in terms of myself and what I would be looking for, more of a single position for someone with experience and marketable skills, and currently holding a full-time job. There's probably some room for improvement in the process for that too, but I don't think the open house idea would be a good fit.
Probably not many, but as was discussed recently in the context of TripleByte[1] some qualified people have "bad" resumes and may struggle to get phone screens. Go through enough resume-level rejections and you might welcome such an open house, if for no other reason than to network with people you might not otherwise be able to meet.
That being said, I also really like the idea.
From a candidate's perspective, the phone screen lets you prove yourself to the company and get to know them a little before taking the commitment of actually going there - usually during business hours, possibly disrupting any job you're currently working at. I feel more comfortable taking time off to go there when they've already proven that they're serious about me and I know that they've evaluated me well enough to know that there's at least a good chance I'm a fit for the position.