Satoshi never told people that the 1 MB limit was to prevent spam - its just what everyone inferred.[/i]
He did express his desire to both intentionally combat micro-tx spamming and to keep the blocks as low as possible in order to get adoption going.
Bitcoin isn't currently practical for very small micropayments. Not for things like pay per search or per page view without an aggregating mechanism, not things needing to pay less than 0.01. The dust spam limit is a first try at intentionally trying to prevent overly small micropayments like that.
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It would be nice to keep the blk*.dat files small as long as we can.
The eventual solution will be to not care how big it gets.
But for now, while it's still small, it's nice to keep it small so new users can get going faster.
Satoshi cared about the wellbeing of bitcoin and he tried to avoid damaging circumstances, whether it was spamming, large blocks, or even ...wikileaks funding.
Basically, bring it on. Let's encourage Wikileaks to use Bitcoins and I'm willing to face any risk or fallout from that act.
No, don't "bring it on".
The project needs to grow gradually so the software can be strengthened along the way.
I make this appeal to WikiLeaks not to try to use Bitcoin. Bitcoin is a small beta community in its infancy. You would not stand to get more than pocket change, and the heat you would bring would likely destroy us at this stage.
As you can see he knew that bitcoin wasn't 100% resilient against all kinds of attack vectors from the get-go, and acted accordingly.
Now regarding your other point:
Okay now we have the process outlined we can analyse the miners incentives/behaviour. I'll be using game theory to explain this and here is where it gets interesting.
The miners main goal is to make profit. This is why he adds tx. to his block in the first place (it allows for more fees and thus, more profits). So we can assume that without the blocksize limit, the miners would add infinite tx. to their block right? WRONG!
Your game theory calculations only deal with actors that are inside the system. They are also projections of our time period to 8 years ago, when money generated from fees were non-serious. I mean even the bitcoins generated were non-serious money.
Actors from outside the system that want bitcoin to die, can spam it to death - AND include the blocks on their own / at their own expense, because the cost of bitcoin back in 2010 was peanuts.
Why would Satoshi allow that? He'd be an idiot if he saw a vulnerability and left it there waiting to be exploited.