Do social networks tend to cannibalize themselves over time? Initially, growth is the most important part of a social network, so it makes sense to prioritize

Do social networks tend to cannibalize themselves over time? Initially, growth is the most important part of a social network, so it makes sense to prioritize usability. Over time, pressures towards monetization mount (either internally or externally, among spammers). Monetization tends to degrade the user experience, creating opportunities for new entrants. Network effects can keep you going, but these aren't Ma Bell's network effects. Users can install competing social apps next to each other using almost no time and less money. They get to keep the more established network as a fallback, then spend most of their time using the one with better features or more "exclusivity." Even if this doesn't lubricate transitions enough for established users, network effects are basically nonexistent among new cohorts (read: the young, emerging international markets). If this is correct, it would explain why no one under 20 actually uses Facebook (or email, for the matter), and why every move from Twitter smacks of desperation. So, I don't know, all hail snapchat? (At least until something displaces that in five years...)