Offer your thoughts or opinion on the input financial query or topic using your financial background.

Is leveraging notoriety to raise stock prices illegal in the US?
Yes, there are legal problems with what he did. To prevent fraud, the US government regulates who can give public investment advice and how they can do it. If you're getting paid to advise an individual, you have to pass certain examinations and maintain ongoing government certification. If you hold a position in a stock you're touting, you legally have to disclose it using particular language. And if you're a corporate insider or hold a significant position in a company, you're restricted on what you can say about the company and when you can say it. Mr. Jackson, aka 50 Cent, held a significant position in the company he tweeted about. My guess is the guys in the suits came to visit Mr. Cent, because if you go to the article the OP links to, at the bottom they mention Mr. Cent's tweet has been deleted and replaced with "go talk to your investment advisor".