One can see the origins of all these little trends that criss-cross between journaling populations—certain surveys only appear among certain populations, etc., but if you look at this page it's almost a random sampling, albeit dependent upon who's doing certain things at certain times of day for certain occupations, or who's in a given time zone. This could be a great tool for looking at what's important to people in a culture, alhough there are a number of confounding factors, as I've mentioned.
I can see why people who start journals or blogs or whatever you want to call them always try to insist upon others starting them as well. After a while spent reading these things, it feels like everything that's important can and should be codified this way. The world is happening here, not in person, and people's writing voices are often more honestly theirs on a blog than in person. There are so many reasons this could be conceivably a good thing.