Blogs went largely unchallenged until Facebook reshaped consumer behavior with its all-purpose hub for posting everything social. Twitter, which allows messages of no longer than 140 characters, also contributed to the upheaval.
Via Ana Cristina Pratas
I thought this article sums up some of the things we have been learning in the course, about twitter, Facebook and even gives the history of blogs. Personally i don't think blogs are on the decline, most people still use their blogs even if they have Facebook because it is different from posting on FB.
Melissa
The success of facebook is that you visit one site and it pushes the information to you... as opposed to websites and blogs where you have to visit several sites to see if a change has been made.