In March, Adi Shamir -- that's the "S" in RSA -- was denied a US visa to attend the RSA Conference. He's Israeli.
This month, British citizen Ross Anderson couldn't attend an awards ceremony in DC because of visa issues. (You can listen to his recorded acceptance speech.) I've heard of two other prominent cryptographers who are in the same boat. Is there some cryptographer blacklist? Is something else going on? A lot of us would like to know.
It certainly seems that way on the surface.