Marc Andreessen’s a16z has just dropped its largest-ever seed-stage cheque of 350 capital letter $M’s into Adam Neumann’s start-up Flow and it feels too funny to be true. Don’t know what I’m talking about? Here’s ten years’ worth of Silicon Valley history in 30 seconds. Marc Andreessen is a fifty-something-year-old co-founder of the infamous dotcom start-up Netscape, and later the co-founder of the first really big and dominant Silicon Valley firm Andreessen Horowitz. Marc is sometimes also referred to as “pmarca”, his Twitter username, and he made billions by investing first money into companies such as Facebook, Lyft, Coinbase, Skype,…