Back in the days before the internet there was a commonly known little scheme that some with questionable ethics would play.  A couple sharpies would go to one of the top floors of a major office tower in a big city, something like First Canadian Place in Toronto.....they would do this around lunch time and as the elevator picked people up on the way down they'd talk in very hushed but audible tones:

"Hey Bob, you hear what happened to Penske"?  "No what"?  "He just got hit with a margin call, overextended himself again, talk is he's gotta come up with a lot of cash or he's gonna be forced to sell out".  "Really, man...last time that happened to him XYX dropped 20 points, what stock is he playing now"?  

The same thing could be done to pump a stock of course....lots of fun and games, the markets can be a cess pool....I don't think anything has changed, its just moved on-line now.