Google dropping siteMaxCpc on Mar'15th to help simplify bid management on Google Display Network.
"We're making this change in response to feedback that having multiple ad group bids for GDN complicates bid management. Most of you using managed placements are already using placement-level bidding to control your costs on GDN, and you'll be able to continue to do this. In addition, content bid (keywordContentMaxCpc) will continue to be available, offering control at ad group level."
Here's how this change will affect you: "after Mar'5th, we'll stop accepting changes to ManualCpcAdGroupBids that modify siteMaxCpc to set it to anything other than 0. After that date, calls that attempt to set siteMaxCpc will return the error BiddingError.Reason.CANNOT_SET_SITE_MAX_CPC.
We'll be announcing this change to all AdWords users early next year but wanted to let you know early so that you can prepare to modify your apps to stop accepting new siteMaxCpc bids. We'll make it possible to "self-migrate" existing managed placements bids by setting them to zero and modifying their other bids as appropriate," explains Google.