I used to work at Goldman's and can tell you that they are paranoid about this kind of thing. They are trying to make an example out of Sergey. We used to get daily updates (on the corporate intranet) about the progress of the case. There is no telling how much money Goldman's has spent going after this guy. Both directly and indirectly through lobbying. You have to ask why, after a year in jail with no conviction, the government still trying to prosecute him? Could it be because Goldman has a very powerful lobbying arm which is particularly strong in New York?
If you are leaving your employer, don't upload any code. Sure. ...but that was over 6 years ago and the guy has already done time. Try getting a job with a prison record. I can tell you that in the banking industry it will not happen.
I wouldn't be the least bit surprised if they keep coming after him. Poor guy.
One last point. There is no market for stolen code. If I stole Google's search algorithm, who would I sell it to? Microsoft wouldn't be interested and it is not like you can take out an ad on ebay. Who would have the brains to figure it out? If you had those brains, wouldn't it be easier to just write it yourself? What is true for Google's code is also true for any complex system such as trading software.