A recent flight I had on an ERJ-175 had 40 1Ks. That was according to the gate agent after I noted how many people seemed to board with the 1K call. More than half the plane.
That reminds me of a flight out of IAD on an RJ-145 that was part of a FT Do that Lucky/Ben was coordinating. There was a bunch of UA Forum members flying and the poor gate agent was totally unprepared for the hoard that queued up when she called for Boarding Group 1. There's been a few FT-related flights on UA that probably were unusually GS and 1K heavy.