Bob Corker's blind trust wasn't blind

Something is wrong with the blind trusts in Tennessee. Senate Majority Leader Bill Frist had a blind trust that wasn't really blind. That's one of the reasons Frist earned a spot in "Beyond DeLay," CREW's list of 20 most corrupt members of Congress. Now, the man seeking to replace Frist, Bob Corker, has the same problem according to the Memphis Commercial:

A blind trust set up to shield businessman Bob Corker from conflicts when he was Chattanooga's mayor may not have been all that blind, record show.

Corker met often with employees from his private companies while mayor from 2001 to 2005, and he shared business tips with others. Corker also got help organizing his 2001 mayoral campaign from City Hall, where a government secretary passed on voting lists and set up meetings for the millionaire commercial real estate developer.

What is so difficult about keeping blind trusts blind?