I’m interested in blogging and writing. So I read problogger, copyblogger etc.

As for commercialization – people earn their livelihoods their blogs. They promote stuff that is actually helpful or else they’ll lose their audience.

a) Commercialization: It’s cycle, A promotes B and in return B promotes A to get C’s attention. Soon or later C will realize it and boycott everybody.
b) People don’t have time and interest to read someone else’s life and stories, the shortening duration of visits is an indication.
c) I would call it an entertainment for those who have plenty of time.