Being too passive.
Recruiters passively run newspaper advertisements, then sort through the resumes.
Top talent, however, is unlikely to be looking in the want ads and will probably have to be recruited from other companies. Recruiters spend time reading HR journals and going to HR conferences instead of learning about their client companies' industries. Recruiters should read industry trade magazines and go to industry conferences then use what they learn as research to build contacts. Asking dumb interview questions. Such queries seem irrelevant and silly to technical gurus.