Back in the mid 80s I ran a BBS (Demented Data Systems) We used to to crap like run scans looking for modems. Anyhow, one of the users found something interesting: an electronic sign on top of a downtown office building here was accessible by modem with no password or anything. Just a banner with the company name, sign location and menu.
He set up a scroll for sometime late one particular evening saying "CALL DEMENTED DATA SYSTEMS - 555-5555 (insert real phone number). So that evening after many beers, the band of drunken ~18 year old geeks went out to the street corner across the road and watched. Sure enough, after what seemed like ages of waiting, there it was scrolling across the screen.
So, yeah, in the olden days some crap was pretty easy to play with.