I have a completely blunt theory on that. People learn that pictures of them smiling in their bathing suit in the Maldives or with that exotic plate of food attract more 'likes' than the pictures of them with that new handbag or handmade watch in their office. So they spend more time eating and traveling and posting pictures, instead of buying that bag. It's what sells. It is no surprise to me that """experiences""" sell likes better than things on Facebook.
If that was true, what determines what people spend money on depends what the dominant social network/ source of news is. Past: magazines at checkout lines: expensive bags and clothing. Now: Facebook: travels and food. Future: who knows what will be the dominant one. But here are my guesses. Pinterest: Hobby Lobby. TMZ: back to expensive clothing. /r/fi: mutual funds. Slashdot: Thinkpads. Hacker News: Tesla cars and Juicero machines. (Let's be honest here, I want a Tesla car and a Juicero machine, so if you have a job that allows me to afford those, feel free to connect, ty).