Sure, I'm not actually in favor of no limits either, but I am in favor of increased block sizes.
Me too.
...right now there are minimum fees that all nodes enforce (not just miners) to prevent spamming
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This isn't quite right, and it's part of the worry. A miner could mine a block that is 100% non-standard spam transactions regardless of fees and it would still be accepted as valid since nodes accept non-standards blocks and miners build on top of them. Blocks #309657 and #309740 are proof of this. The spam filters are achieved with the isStandard() method call and only prevent nodes from relaying transactions without the requisite fees or those that include dust outputs--these TXs can still get mined though.
In case anyone's interested, currently about a third of the UTXO database is spam (a lot from SatoshiDice before the dust limits were implemented).
