One of the more intriguing provisions of the new post grant patent proceedings of the America Invents Act (AIA) is the ability to settle these patentability disputes by agreement. Unlike existing patent reexamination practices, the USPTO will terminate an Inter Partes Review (IPR), Post Grant Review (PGR), or Transitional Proceeding for Covered Business Method Patents (CBM) upon joint request of the parties. (cf. terminating an inter partes patent reexamination by operation of estoppel).
At the time of writing, several such disputes have formally settled, some after trial institution (here), and some a mere weeks after petition filing (here). As of yet, I am unaware of a challenger that has simply walked away from the PTAB proceeding in the interests of maintaining the absolute confidentiality of their settlement agreement.
The USPTO greatly benefits from the ability to terminate post grant patent proceedings. This is because agency resources can be moved away from proceedings that are no longer commercially relevant (as to the present parties) to those newly initiated. In this way, the USPTO would operate in much the same way as a court, no longer being responsible for continuing the patentability proceeding on behalf of the public (as is the case in patent reexamination)
The practice of fixing a claim construction for key terms in the Order instituting the patentability trial is also a key driver for dispute settlements much the same way as a Markman Order. As such, it is not surprising that the PTAB has made claim construction a focus of early Orders.