[BC] Restrictions On Assigning Call Letters

[Tom Dimeo]

Early this morning on 3885 kHz I heard a ham station with the 
callsign of W4TIT.  I thought for sure he was a bootlegger 
but he was not.  The callsign is a valid one.  Of course, it 
is a vanity call.

That got me to wondering if there are any restrictions on 
callsigns either ham radio or broadcast stations that the FCC 
assigns?  It seems to me that this one shouldn't have been 
allowed.

Tom, not necessarily a prude.