Today the Ninth Circuit, in Busk v. Integrity Staffing Solutions, Inc. (9th Cir. April 12, 2013) joined other circuits in concluding that FLSA opt-in collective actions are not incompatible with state law claims asserted as Rule 23 class actions:

In sum, we agree with the other circuits to consider the issue that the fact that Rule 23 class actions use an opt-out mechanism while FLSA collective actions use an opt-in
mechanism does not create a conflict warranting dismissal of the state law claims.​

Slip op., at 9.​  I will write up a bit more later, but this holding should put an end to the wasteful motion practice around this issue in the Ninth Circuit.  Given the agreement manifesting between the Circuits, it is unlikely that we will see Supreme Court review of this issue any time soon.