The version of the Clipit applet in 14.04's repos has an "offline mode" option. It is not really clear what it does, as Clipit seems to lack support for any Pastebin site. Any ideas?
Offline mode means, ClipIt doesn't save your copied text in its history.
Start a test
Copy some text by pressing Ctrl-C with disabled offline mode and you can see your copied text in the history (click the ClipIt icon).
Now activate the offline mode, copy another text and check the history again.
You can see, there is no entry for the copied text.