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<p>their signatures on the bottom of a letter of recommendation don't carry as much clout as a professor's signature.</p>
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<p>Profs will generally sign letters drafted by their TA's.</p>
<p>IMHO, TA's should not be the ultimate authority in a course -- there ought to be a very experienced person students can turn to if there's a problem. On the other hand, I don't see the evil when TA's supplement the professor who actually teaches the course by leading discussion sessions or running labs.</p>