[Nyororin]

You might want to check the rules. Specifically this portion;

4 - Creating a new thread:

4.1 Search before starting a thread. Your thread might be edited, or deleted by a mod if there already exists a thread covering the same topic.
4.2 Don't start pointless threads. Threads created out of boredom, or because you want to be "random" are not allowed. There will be no "chat" threads (besides "The Chat Thread!"), randomness threads, or boredom threads.
4.3 Use a title that accurately represents the content.
4.4 Game threads of any kind are not allowed.
4.5 Looking for friends is encouraged on Japan Forum, but posts looking for boyfriends, girlfriends, or anything beyond platonic relationships will be deleted. Make friends first and let nature take its course.
4.6 General Discussion is for threads that don't fit into any of the other categories. HOWEVER that does not mean that any topic is appropriate for General Discussion. Along with following the above rules, General Discussion threads should be
1) Relevant and inclusive to a majority of JF users
and/or
2) Timely and current (i.e. related to upcoming holidays, news or events).
and/or
3) Japan/Asia related.

Now... Think back to the threads that disappeared. Were they "I am so bored!" or "Lets make a list of such and such!" or something completely random and clearly made out of boredom? You will receive your answer as to why they disappeared.