It doesn't matter. His primary goal in giving the talk himself was probably not so much to teach people about memcached, but more to signal his values, one of which is that Facebook is a company where technical contributions are highly regarded.
Yeah, I guess the main point here was to have the CEO give a TechTalk - which fails. Of course showing half of your companys employees during your presentation might be very motivating but if you mess up the tech part it just ends up being weird.
I love memcached so much, it's totally saving my butt right now. This was a pretty interesting talk, but I don't think Zuck should have been the one giving it. He needs to give his talent more room to showcase their talent.
Why is he giving this talk? I don't believe he fully knows what he is talking about. Seems like he is just following a presentation someone else prepared for him.
RAM is disproportionately expensive on leased/managed servers; afaik it's just the pricing model that hosting companies established in the past (when RAM accounted for more of the total hardware cost compared to now), and the industry has stuck with it.