I can't speak for PG, but I think the general idea is that a slow influx of new users is less likely to alter the nature of HN as everyone has a chance to acclimatize (avoiding some sort of Eternal September), and the people who really "need" to be on HN (people interested in startups I guess?) will know about HN already, or be told about it. That last part might be a little "fightclub-ish" I guess, but it seems to be working alright.
Couldn't he just turn off registrations for new accounts? Not saying he needs to get HN to the top for a "startup" search query. I found HN by a Google search while looking for a good laptop to run Linux on.
That happens. When too many people register accounts they're locked for the rest of the day and the register account option is no longer there, only login.
IIRC (I might search for it later) that was a spambot fix. Apparently it was fairly effective - I presume the bots were smart enough to find the 'login' link on the front page then register an account from there but not much else.
