Very annoying. If you are using WordPress for your new project and realise that the wordpress toolbar is displayed to logged out users it is a very annoying situation. But why? You have never seen this happening before why is this happening now? How do you hide WP toolbar?
Have you installed plugins recently? Here is what you will do. Disable all plugins, then start enabling them one by one (has the toolbar disappeared when you disable all plugins?). After enabling a plugin, check the appearance of your site. Make sure you are browsing with another browser where you have not logged in and you see the site as a logged out user. Probably one of the plugins will cause that toolbar to appear again. In my case it was the buddy press. I had the turn off the display of this toolbar from the buddy press’s settings.
Hope this helps.