On Wed, Jul 17, 2013 at 2:37 PM, Tamas Blummer <tamas@bitsofproof.com>wrote:

> A majority coalition of miner (pool operator) might even decide to change
> block reward
> rules if the rest of the network only verifies POW.
>

Which is why it's still vital that any "important" node in the economy uses
full validation.

A majority miner coalition could change the block reward and award
themselves money which SPV clients would accept, however, the moment
somebody tried to cash that money out via an exchange, or use it to
purchase something from an online shop, or just see if it propagated across
the P2P network effectively, they'd notice something had gone wrong. Of
course it'd be in the news long before this happened ....

SPV is really meant for nodes that go away and come back a lot, i.e. end
user wallets. If you're a merchant it'd be dumb to run one unless you're on
such a tight budget that your server resembles a powerful tablet.