The researcher is lucky that TradeKing believed their NDA trick was sufficient. Even if the case here is weak, and I wouldn't necessarily assume it is, it would still seriously damage the researcher's life.
Here's how it goes when you get sued by a big company. Their lawyers essentially have a heyday doing everything possible to obstruct and delay the process so that they can maximize their time on the corporate teat. It will go on for years; they won't mind because it's business as usual for them, and they're getting paid big bucks to torment you. Your life will be ruined: assets seized pre-emptively, reputation and credit destroyed, inordinate quantities of time consumed by legal research and tedious paperwork, struggling (if not immediately blatantly failing) to keep your incompetent counsel paid at $250/hr and meet the retainer, and eventually failing to file some document or pay some fee that will cause the court to enter a default judgment against you and permanently confiscate everything you own, leaving you with the albatross of a massive outstanding judgment waiting to be enforced, bank accounts garnished any time you get any money, etc. And that's the short version!
And then guess what -- if, by some miracle, you don't lose in the first round, this whole process will repeat as they file appeal after appeal. Hunker down because the proceedings will last at least 5 years.
The corporate lawyers will be able to justify all of it to their clients without blinking an eye, who probably forgot that they even asked them to sue you. Everyone at the company and the law firm will go home and sleep soundly on their piles of money, and you'll have learnt your lesson that trying to stop the subterfuge of an online trading platform is a terrible offense.
Good reading: http://www.nissan.com/Lawsuit/The_Story.php
IANAL.