Constellation Energy dropped 10% in the span of seconds as bids disappeared following this headline on December 21st at 11:58 AM

US sues to block Excelon acquisition of Constellation Energy

Trading is halted in CEG five minutes later and reopened at 12:08. CEG rockets up 10%, and at 12:10 a headline crosses saying,

US settles with Excelon

Themis Trading, a stalwart critic of HFT, attributes the activity to the shady business of machine readable news.