It seems like this should extend to many other roles as well. If someone in the EPA has investments in energy or manufacturing, for example. If someone in the FCC has investments in tech or media conglomerates. Pretty much anyone who has access to information about changing regulations, enforcement, etc. before the public.

Congress has been known to have above average returns on stock investments, making the congressional salary increases we quibble over look like chump change, if they are using their unique knowledge of policy direction to the fullest.