A few days ago i was trying to do a search on dev but the facets were broken, i think because there were too many of them, making the GET request too big, so i added a bunch of not so interesting fields to the search_excluded_facets
pref.
title_initial,title_firstword,tracker_field_f_39,tracker_field_last_modified_by,tracker_field_importance,tracker_field_ease,tracker_field_securitySubmittedBy,tracker_field_securityAssignedTo,tracker_field_securityDateReported,tracker_field_securityFixDueDate,tracker_field_securityActualFixDate
There probably should be some sort of self limiting mechanism, possibly to do as part of the search front end revamp i've heard talk of (but can't find a page about)