I have a solution: divide everyone into two groups arbitrarily. Then, tell everyone to look at everyone in their group, and inform them they won't be able to t

I have a solution: divide everyone into two groups arbitrarily. Then, tell everyone to look at everyone in their group, and inform them they won't be able to talk to any of those people. Then offer anyone who's unhappy with this (because they see someone in their group they'd like to chat with) the option of switching sides. Do it one at a time, until everyone's happy with the arrangement (however long this takes), then if one group is too large, arbitrarily move some people to the smaller group and repeat. When time runs out (because you've booked the venue for X hours), then send everyone home even though they never actually got to do the speed-dating at all.