I wouldn't call it politeness. Japanese users are adhering to a social contract about communicating e.g. "excuse me" when messaging strangers, etc. If you don't follow those informal rules you'll get dunked on. >>4
MAD/blog culture is dying especially with niconico getting overshadowed by Youtube and Yahoo blogs getting abruptly shut down like geocities. New sakura.ne sites are dwindling and ameblo is only held up by celebrities. As I see it accessible mobile-friendly apps like Twitter are still at the top. Yahoo answers is also surprisingly active.