I have another related theory that goes: Over time, everything converges into mediocrity. By everything I mean products sold to us, entertainment, media, the Internet itself. Look at the car designs of the 1970s and now. Look at cinematography then and now. As soon as marketing steps in and start telling otherwise innovative companies or artists how to sell, things begin slowly converging into mediocrity.
The semi-formal proof is that because the humanity as a whole is mediocre almost by definition, hence if you want to expand your markets (the ice-cream saleman's problem) you'd grab the middle of the bell curve first: it's where the bigger part of the market is!
I don't know if it makes sense, just something I've been thinking about a lot lately.