3. How should the white-collar criminal in this story be sanctioned? (explain also why have you chosen your method of sanction).

Obviously, Seth and the others involved in this criminal activity of selling artificial stocks for artificially inflated prices should lose their Series 7 licenses. That would prevent any of them from trading of stocks of any kind ever again. This forfeiture of their professional rights as stockbrokers is entirely necessary in order to prevent them from victimizing others by creating other shell companies or hatching any similar stock-related schemes. This is especially true in the case depicted in this movie, because they are so young, and this shady business, clearly, is their only profession.

They should all also serve time in a federal penitentiary facility. The particular criminal sanctions against them would have to depend on what they were charged with, and what they were then convicted of. As first-time offenders, plea bargains would be likely, but they should all still be convicted of felonies, which would sanction them in many ways, for life in fact, even after they finish serving time. Grand theft (theft by deception) comes to mind as something with which they should...

For that offense, they should definitely all serve as much time as possible, depending on sentencing guidelines for whatever white collar crime(s) they are convicted of.
I have chosen these two means of sanction in particular because (1) these sanctions would prevent any of them from ever re-offending in this manner; and (2) once they are released for prison, now that they all have felony convictions, and with all of their Series 7 licenses revoked, they would next be forced to find (probably much lower-paying) work outside the financial sector. (This seems good "poetic justice" as well, especially given the greedy, acquisitive nature of their crimes.)

Work Cited

Boiler Room. With Giovannini Ribisi and Vin Diesel. New Line Productions

(DVD). 2000.