This is a great analysis although the Silicon Valley jargon is heavy at times. Even as a fairly-regular HN reader, I didn't recognize some of these, like IAC and ARPU, and they aren't defined or linked in the piece.
Pretty sure IAC is the massive holding company (iac.com) that owns multiple dating sites, and not a business acronym. Weirdly, a quick perusal of their site doesn't indicate what it stands for.
IAC has basically stopped treating its name as an acronym and now just calls itself IAC, but it originally stood for InterActiveCorp.
IAC is the name of a company. ARPU = Average Revenue Per User