Not all to surprised about this. Makes me wonder how many others are doing this sort of thing that have not gotten caught yet.
It has happened, and is surely still happening, more often than we could know. Which is one of the reasons we try to cut down on the information we expose to companies. Even well-run one's can fail to detect a bad apple, someone falling on hard times and being desperate for money, or someone being blackmailed.
Indeed. And how many of them are in the TLAs. And how many of them can use privileged insider information (insider dealing for example on the spread-bet market). Virtually undetectable on a small enough scale (as opposed to the institutionalised insider dealing they doubtless get up to). I always felt the opprobrium on Snowden was rather rich, because I reckon more venally motivated colleagues have probably sold the same info loads of time, and are still doing so.