For example: blow the whistle on the largest tax evasion scheme in history: go to jail. Participate in largest tax evasion scheme in history: no problem.
If we're talking the UBS case that others have alluded to here:
He went to jail because he didn't tell the whole story and tried to cover up his part. Whistleblowing rules require full disclosure of your information to prevent them just being used to take out rivals; by covering up his part in the illegal activity, he forefeited part of his protection and so is in prison. This is normal and perfectly fine.
If this is the UBS guy, the hole in your statement is he did both and went to jail for the latter. He was whistleblowing on his competitors while actively trying to hide the assets of his clients.
