Perhaps so many people want to use RTB4 that there are too many people for the master server to handle?
Or RTB4 had so much stuff all the people having it is overloading the master server.
After reading what Ephi said, I understand it as:
-People want RTB4 because its cool.
-RTB4 server crashes.
-Everybody restarts Blockland a ton to get it to authenticate.
-That then crashes Blockland's Master server.
-Now we are all sad.
I might be wrong, but that is my summary.