I have compromised very large organizations as deeply as you can imagine, easily covering things that would permit insider trading etc. The truth is we operate at the highest levels of discretion and it just isn't an issue.
The SEC is very far from my radar, and, like anyone else with privileged knowledge about things a company might due that would impact their stock price, you just don't act on it. It really isn't hard to avoid.
Government agencies will not beat down your door, but they will definitely hire you if you have the right skills. It isn't a one way street, though you can encumber yourself. (For reference, look at famous guys like Charlie Miller, who came from the NSA).
You don't learn one thing about the world. You learn how brittle software is and how terribly insecure most things are. And along the way, if you let it, this can make you a bit cynical. Breaking software becomes like breaking a child's toy in many cases. It is still a lot of fun to break things.
When a TLA offers you a job, or a contract, you can decline. There are no hard feelings.
This is the most terrifying item on your list. Saying no, however, is generally the best way to avoid such a one-way street ;)
Things that can happen:
- you manage to break some stuff during pen test that nobody expects and learn things that make you become a liability for that company
- you might learn some things about company whose stock price can drasticaly change and you will need to answer questions to SEC (or a similar institiution)
- if you are really good, it's quite possible that government agencies will try to recruit you, and if you say YES, it's a one way street.
- you may learn some things about world you wish you never learned about, and you wouldn't be able to watch the world with the same eyes ever again - even if you wish you could