Did Satoshi Nakamoto (in his blogs or the whitepaper) forecast that mining pools would exist? Mining pools are common today where users pool their resources together and share profits accordingly. Such pools today can account for significant proportions of a network's hash power and they're are risks shold a coalition of malicious parties form a pool with 51% of the mining power.
My question is, did Satoshi ever forsee this coming or consider it as a possibility that may arise? Did Satoshi ever provide any thought about the positive/negative implications of the existence of mining pools?
Nakamoto did discuss the idea when others brought up the notion of cooperative mining, but I don't know if he wrote about it before anyone else came up with the idea.
You can search an archive of Nakamoto's communications
https://satoshi.nakamotoinstitute.org/posts/bitcointalk/threads/250/?view=satoshi

ribuck's description is spot on.
Pool operators can modify their getwork to take one additional parameter, the address to send your share to.
The easy way for the pool operator would be to wait until the next block is found and divy it up proportionally as:
user's near-hits/total near-hits from everyone