Interesting excerpt from Startups Open Sourced on this:

Q: How long did it take to get the beta version of reddit built?

I think we launched in June, a little less than a month after we got started. It was a really rough version of the site and it was basically a version that we just finally got online because it was tough. It's not like there were a lot of people clamoring to see what we were about to do. We were just two random kids out of UVA. There were people who were curious to see what Y Combinator was going to produce, and it helped being the first YC company to launch.

To get that initial traction we benefited from those Paul Graham fans that were just curious about what Paul was doing, what YC was doing, and Paul made sure to mention us whenever he was talking about Y Combinator. A couple of his early essays helped out because he would link to us and, certainly, having Paul Graham readers as your first users on a social news website is a great asset, because the links that they are going to submit are generally high quality and pretty thoughtful and so it sets the tone very nicely.
As for growing it outside of that, I begged a lot of my friends and I definitely emailed that old list of folks from that PHPBB forum, announcing it. But the rest of it was just a lot of grunt work. Every time someone wrote a blog entry about reddit—and this is, of course, pre-Twitter—good or bad, I was going to leave a comment there and engage them, talk to them, make a note of them. I just worked my way up the food chain, so to speak. The funny thing is, nowadays, TechCrunch is considered the place to launch your site. reddit never got a single mention on TechCrunch until the day we got acquired.

I always stress to startups that they shouldn't be building and working for TechCrunch appearances because those don't really mean anything in the end. You can still have a successful startup without ever having a write-up on TechCrunch, for instance.

Q: Did you build fake accounts to get user growth early on?

Yes, I've said this publicly, usually to some laughter. It certainly helped. This was also one of those things that fell within the purview of the non-technical founder. Steve made this nifty little way—a form field—for us to just type in a random username that came to mind, along with the URL, and the title, and that's who it would be submitted by. That definitely helped, but it really only mattered for the first three weeks, and then there was some point when Steve and I didn't actually have to do anything, and we were so thrilled.

We didn't have to submit or vote; there was no commenting back then. The site just worked, and the trick with a social site, especially one like reddit, is: if people come to it and it's empty, the incentive for them to want to contribute to it is really, really low, especially when it's a totally new thing. Even now, when new reddits are created all the time, it's really tough to feel interested in submitting to a lonely, empty new reddit, but once there is a little bit of momentum, once there's a few new users, there is some social proof and this is now what, six years later?

Back then you show someone an empty reddit and they just see a blank website and they can't even comprehend what or why they should ever consider participating in this, so I really have no qualms about having done that, in the beginning. It would have been a different story if we had commenting and I was writing comments like, “What a brilliant comment, Alexis, your genius is unmatched!” That would have been crossing the line. And obviously fake.