I have noticed that there have been a lot of bumps in the digital goods section that are done more often then every 24 hours. The solution to these is to report them to get them deleted (this part is easy).
I have also noticed that several threads seem to get random people asking random questions in threads and then never coming back to the thread, nor appear to have any actual interest in what is being sold. From what I can tell these posts are made at approximate times where the thread would appear towards the bottom of the first page or somewhere after the 1st page; not only that but the original poster will not respond until the thread will have fallen to a similar place (I have not had a chance to do a study on this, I was planning on doing so, however it seems that bump spam has gotten worse in recent times)