Adam Back (from this excellent block-size controversy overview):
I believe that the unstated different assumption – the point at which views diverge – is the importance of economically dependent full nodes. It seems that Gavin [Andresen] thinks a world where economically dependent full nodes retreat to data-centers and commercial operation – and basically all users can only get SPV* security – is an OK trade-off and cost of getting to higher transaction volume a year early. But most of Bitcoin’s technical experts strongly disagree and say this risks exposing Bitcoin to erosion of its main differentiating features.
* Simplified Payments Verification, as criticized by Peter Todd (in the same article): “SPV nodes and wallets are not a trustless solution. They explicitly trust miners, and do no verification of the protocol rules at all. For instance, from the perspective of an SPV node there is no such thing as inflation schedule or a 21 million bitcoin cap; miners are free to create bitcoins out of thin air if they want to.”
Back debates Andresen on the block-size question.
(Transcripts from the weekend’s Bitcoin Scalability Workshop in Montreal are available here.)