AFAIR you can. It was left in there when we removed a number of the other dll's for optimisation purposes as it can be enabled as an option via the host menu, and will break your site if it's enabled and the files not there as it's referenced as part of the membership provider. If you are the only host then it's probably safe, otherwise I'd edit the admin\host\hostsettings.aspx page and disabled or remove the chkUsersOnline checkbox

sorry for the latest of my reply, i've been travelling on business.

In this case, you can. Both of those use the logging provider, which reads from the config file, and only attempt to instantiate any files that it's configuration directs it to.

Cathal