We recently ran a poll in conjunction with the Ubuntu Design Team to seek out your preferred option for the default Unity launcher behaviour for multi-monitor usage in Ubuntu 12.04.
Almost 13,000 of you voted in that poll, and, based on those results, a decision on the default behaviour has been decided by the Ubuntu Design Team.
By default only one launcher on one monitor will be in use in Multi-Monitor set-ups. An option to enable the launcher on every monitor attached will also be available, so if the default set-up isn’t to your tastes you won’t be left crying.
Work on landing the code for the new multi-monitor behaviour is now underway.