The question of whether definitions matter when one sub-category or subset is a minority or majority... I’m not sure how to answer that. Why would a definition stop mattering just because something different is a small subset? I must assume that a categorical term includes everything in the category. If you don’t mean everything in the category, then don’t use the term that refers to the category. If you mean phone, then say phone. ?? Right? I’m confused why you would argue anything else.
I don’t see how that data is all that valuable. There’s the inherent network effect of needing to install it to send/receive money from a friend who did.
But a surprising number of people will pay for instant transfer(almost all of that 300m probably comes from this), and the debit cards they get to take in a portion of the merchant transaction fees. They’ll probably be profitable off that, with p2p as a loss leader to drive installs
Furthermore, just because you can link people together, it doesn't mean that knowledge is actually valuable. The only social network you can link to Venmo currently is Facebook. The only other way to "discover" contacts/friends is by uploading your contact book to Venmo's servers.
I'd say that Pubsub has it's own use cases, as it provides different guarantees than Kafka (most importantly in message ordering that enables different performance characteristics).
I started programming at 15 after getting into custom WarCraft III maps, went from a GUI Interface to JASS (WC3's scripting language) and finally started using C to make my own small mini-games, I imagine it's not an uncommon path among young people that want to be game developers.