This really can depend on your system and the type of splitter that you are using.
Here in Gainesville, we use terminators for three reasons:
1.) To prevent ingress from entering the system through an open port at the tap.
2.) To prevent signal reflections (which really isn't too big of a problem).
3.) To prevent cable theft.
Honestly, I doubt it would make much difference to have a terminator on a splitter in the home. If you want to do it anyway, you may be able to pick up a pack or something from Radio Shack.
You cannot use the ones that cable companies use, because they require a special tool to install/remove them (prevent cable theft).
Please see the definition for terminators for pictures of them.
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