In a 2-1 decision issued today (copy here), the Third Circuit Court of Appeals ruled that the National Labor Relations Board lacked the authority to act as early as March 2010, when President Obama appointed Craig Becker to the Board. The Third Circuit held that Member Becker's appointment to the Board while the Senate was on an intrasession recess (a break within a session of the Senate) was unconstitutional. Implicit in the court's decision is that the appointments of Members Block, Griffin, Flynn in 2013, while the Senate held pro-forma sessions, were also invalid.
The Third Circuit ruled that recess appointments are only valid if made during intersession breaks (i.e., between sessions of the Senate).
If you do business in Pennsylvania, New Jersey, Delaware, or the US Virgin Islands, the net effect of this decision may be that, until the Supreme Court rules in this pending case, you can basically ignore just about anything* that the Board has done this decade (well, since March 2010).
* From June 22, 2010 through August 27, 2011, the Senate had confirmed enough Board members for quorum. So don't ignore that stuff.
(h/t The Volokh Conspiracy)