In addition to price manipulation, if it was legal you could easily and cheaply transfer gains from high tax jurisdictions to zero tax jurisdictions.
To create artificial volume to pump and dump pennies. Hit the bid with volume to bring it down several levels where there is another of your accounts holding it level while other buyers come in after the news hits lifting your offers to create greed. ;o) rinse repeat.
Got that 1 wrong, but still what normal person's got the volume and time and commision charges to play that kinda game with pennys. Also wishes I'd of thought of this, 20 years back while playing pennies! LOL
Stock promoters selling multiple levels higher on the offer all the way up from stock that was DWACd into their account prior to a pump and dump program commencing.