I thought the comment about how google is experimenting with CPA by converting to CPCs was quite interesting. Your live notes seems to skip that. I think he gave an example about how a $20 CPA could be converted to a number of CPCs at the regular CPC price of $0.4 for that keyword. So the advertiser would have an option of bidding for CPA or CPC, but internally it gets converted to CPC. He mentioned that this provides a lot more granularity.
I think this is a lot smarter and granular way of going about CPA, rather than the 60-day cashback that MSFT is offering.