The first chatter to use it was in fact only replying to a string of illeterate shouts people were making on purpose to make fun of famous qoutes and the ORLY fad, using several times leet (1337speak).
The meanings can differ. But the original meant "Bitch, you fail."
Then next time it was used, by the same chatter, it was trying to tell the person that was subjected to the use of it to get over his/her problems.
There are also some vague meanings floating around, but these were the two most common.
"insert rant, pointless whining or attention seeking" - person 1
"Beech go boom already." - person 2