I would say so long as it is clear there is no one master corporation, there should not be too much issue from players introducing themes relating to them. There are surely some megacorporations of course, ones that are the real titans, but a gambit of everything vying for those upper tendrils of power and niche roles should be fine. Generally the only thing I would urge us all to stay far away from is power creep of any sort, say any of our characters being more, if involved in a corporation of course alike anything else, being mid-level at best. Not an executive, but a supervisor or manager; a boss, but not one [i]the[/i] bosses. Likewise, a gang enforcer but not the criminal leader, a police sergeant or detective, but not the captain, so on and so forth.