"Seminar callers get their name from the seminars they attend to learn how to most effectively get their message on the air."
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The above snippet is from Wikipedia's definition of a "SEMINAR CALLER". This type of caller (person) is not viewed as a 'positive' but rather a negative, due to the covert nature of masking who and what they are really about. Rush continually mentions seminar callers -- and one gets through his screeners every now and then -- :-)
If they get through, they are generally allowed through. I have noticed that he is allowing more through over the last several months.