The fees currently paid, even for first block inclusion while 'blocks are full' are near zero.
Urgent first block inclusion right now costs 0.03 USD and if you want to go +1-3 blocks, you can drop that to ~1cent. Spamming the blockchain is, for all practical intents and purposes, a very low cost activity.
Why would the miners not simply ignore these transactions?
@roughly 3tps x 60 x 10 = ~1800transactions x 2cents = $36 added to ~$10,000 block reward, making it $10,036?
Is rational self-interest = shitting where they sleep?
I believe they're just keen to solve those blocks before the other guy does it. Innit?
If solving a blog earlier means BTC price falls (as it would, if teh blogchain becomes too bloated to be practical), then solving a blog earlier don't count for shit.