Earlier quoted context omitted.
Reddit's a unique case because their initial user base (like News.YC's) consisted of other YC founders. And since they couldn't afford any form of promotion that cost money, news of the site spread mainly from those users.
I'm finding it difficult to square your assertion that Reddit is "unique" in this respect with the assertion that it's the web that's "making marketing and distribution free". The only way that web marketing is "free" is if product awareness spreads between customers, or is pushed through the founders' personal contacts. Wouldn't this imply that we could expect this phenomenon - the initial user base being in some wa…
Awareness of Reddit did spread between users.