Even the 30+ million is not relevant, Facebook with already have all of those users. So they didn't buy any users, no revenue, no profit, just some technology which they much have been able to build themselves for a fraction of the price.
30+ million users relevant to Facebook? Of course not.
30+ million users relevant to a talk about scaling? Absolutely. The title of the article is "How To Scale A $1 Billion Startup" - but it's a tech talk about how to scale to support their userbase, not a business talk about how to increase quarterly profits. Hence, the number of users is far more relevant to the discussion than how much they were bought out for.
It is relevant since this was a technical talk. The speaker didn't even mention the Facebook acquisition; he just said that they've been in the news lately and can't talk about it.
