The overwhelming number of near-useless, tautological replies to this question here and elsewhere is pretty disappointing.
Here is what I discovered, buried inthis bug report on Sun's Java community:
"This object is responsible for a propagation of Java Plug-in settings from admin account to all regular (non admin) user accounts. In other words if SSVHelper is registered with IE then the only thing admin needs to do in order to switch from a new Java Plug-in
to an old Java Plug-in is to run from a command line: ssvagent.exe -high -jpisetup -old or uncheck a checkbox "Enable the next generation Java Plug-n" in Java Control Panel. In both cases changes will be propagated to non admin user accounts."
Therefore, if you are not in a managed, Enterprise environment—as in, this is your own personal computer—then the SSVHelper Java Browser Helper Object does nothing useful for you, and can be safely disabled.
I know this old but I'm posting anyway because people still use the information in these posts. It not necessarily true that if you are using a personal pc without being in a managed environment that you don't need the plug-in. There are
some sites that use the plug-in so its a good idea to keep it. If you find it in your browser there's a good chance it's there for a reason.
I removed mine a while back and it caused multiple problems in browsing my regular sites. I don't which sites use it but once I put it back every site I frequent worked fine again