Employment class actions have been dealt a blow by the recent decision in Dukes v. Wal-Mart. You can look at the decision here. The decision, as I understand it, finds a lack of "commonality" among the female plaintiffs because there is no one company policy that caused their discrimination. The "policy" the plaintiffs were relying on was actually a lack of policy. Wal-Mart lacked protections in place to keep local store managers from discriminating against women. I have previosuly discussed this case here and here and here.
Bu, as several lawyers have pointed out, the facts and evidence from Dukes v. Wal-Mart will surely continue in localized class actions. Class actions can be any size from a handful of potential employees to thousands. So, the Dukes v. Wal-Mart case will likely become several state and region class action lawsuits.
Commentators talk about how this is the biggest employment decision in the last ten years. Not to say it is not an important decision, but, really few of us plaintiff employment lawyers do class actions anyway.