And why are they called that?
They’re not called hampsters. 
There is a running joke that because this board is so slow sometimes, it must be powered by hamsters running on a little wheel. That’s all.
They are the hamsters that run around in their little hamster exercise wheel to power the straight dope message board.
This is a pretty old joke about underpowered things in general. When I was but a wee tyke we made jokes about the underpowered school bus. Like the hamsters are tied today etc.
Of course, when a post disappears the only logical explanation is that the hamsters ate it. It’s frustrating when that happens, but the only other possible scenario is that gremlins did it, and hamsters are much cuter than gremlins.
But occasionally they eat it, and then vomit it back up repeatedly, to make fantastic double and triple posts. I think I remember seeing a quadruple post once or twice, and one time when two people double posted “around” one another i.e.
Post A
Post B
Post A
Post B
Those darn hamsters! 
The question has been answered, so I’ll close this thread. For future reference, questions about this message board go in ATMB.