I currently own a server with about 40 players at peak times, and there are these few players who build MASSIVE factories out of BuildCraft pipes. I have looked through all of the config files of Buildcraft and even tried de-compiling it's source code. Is there any way to prevent this without banning the pipes? I am using Tekkit Classic.
There are a few ways to combat this
upgrade to logistics pipes they are a lot smarter although a little more expensive.
Request that users put obsidian void pipe overflows where the item drops may occur, best way to implement this is to supply them to the users.
Use OP commands to delete entities on a schedule say once an hour. (can be problimatic when people drop items at the wrong time so set a warning message up) Can also be implemented with bukkit plugins.
ask people to use pipe converters to change pipe type at end points of the system. thus being cheaper than changing their entire pipe system.
To my knowledge these are the best options for working this issue out.
I hope this helps. if anyone would like to add to this list feel free.