Here’s a 2011 HN post describing that claim about an unscalable feature in more detail: https://news.ycombinator.com/item?id=2370291

(That was linked from http://highscalability.com/blog/2007/11/13/friendster-lost-l... but I had to fix the link, since it went to apps.ycombinator.com which must have been the HN URL at the time. Maybe dang can update DNS to make those old links redirect? Everything after the host was still correct.)