From time to time, RfM has threads asking posters what their "last straw" was, i.e. what happened causing them actually to leave the church (to resign or immediately stop all activity.) I expect that in the future, some of the posts on RfM will say, "BKKKP's homophobic Oct. 2010 General Conference talk."
We know that some members have left because of Packer's talk. We just don't know exactly how many!