I want to get into startups, but I don’t know where to start

I don't think it is fair to expect you to talk about your old company's codebase in an interview--I'd love to have that conversation, but I understand if you wouldn't feel comfortable doing so.

So, I can ask you questions in person, and get some response. Maybe you interview well, and you can answer things easily; maybe because you know your shit, maybe because you crammed with "Crack the Coding Interview"-like books, maybe because you have inside information on what'll come up in the interview.

Maybe you interview poorly, and if I ask you to whiteboard something you have a panic attack even though you know it cold. Maybe you are having an off day, or our conversation just flows the wrong way and you don't communicate to me the experience I'm looking for that you already have.

By contrast, if I have your github (or sourceforge, or bitbucket, or whatever), I can infer certain things about you: I know what languages you write in, I know whether you roll things from scratch or make little changes to other people's projects, I know how much you care about code quality and commits, I know what sorts of projects you like to work on in your free time.

In an interview, I can (and will!) ask you about some code that you've written, both good and bad, and I can see how you respond--are you defensive, apologetic, humble, humorous? I can ask questions about specific projects, work through your thought process, and get a much better feel for how you are on a team.

As to your question "What is the difference between experience writing proprietary code and experience writing code that happens to be published on GitHub?"

The difference is that I know for certain you can use git, I know that you aren't hiding behind your team on that project, and I know what lines of code you did and did not write (barring certain corner cases). Proprietary code is also usually pretty fucking dull, honestly: you're usually patching or hacking in some business logic for a legacy app that isn't that great to begin with. If I cared about that, I'd just hire some legions of code monkeys from India and be done with my problem.

Here in the UK we have a startup job fair called Silicon Milkroundabout [1]. At the moment it's London-based, but it attracts a huge amount of college grads. I suspect they'll soon be moving into doing or taking part in job fairs at Universities around the UK, because they're growing pretty quickly at the moment.

Maybe they also need to start making their way into the US, too.

[1] http://siliconmilkroundabout.com/

So, pretty much any business? There are so few companies out there, especially venture backed ones, that the employee headcount hasn't scaled with the growth. We just hear of the Instagram/WhatsApp acquisitions with low head count so often here in the echo chamber that we assume it's norm. To take that further, how many companies are at FB/SalesForce/WorkDay/Twitter-level that don't have over 500 employees (much less 1,000s)? I can only think of very few - 37signals, Valve, etc?

My larger point - VCs in SV want to fund billion dollar businesses and founders who can create billion dollar businesses. These billion dollar businesses need large amounts of headcount and a CEO who can take them there.