if everybody solo'd then the difficulty would be such that solo mining would be profitable, right?
isn't that what satoshi *really* intended?
Pools don't change difficulty or the total network hashing power.
9TH is 9TH.
Another way to look at it is the block susbidy is 50 BTC (until they cut). The network tries to keep block time at ~10 minutes so there will be about 6 * 24 * 365 = 52,560 blocks per year.
52,560 * 50 = 2,628,000
The network attempts to payout 2.6 million BTC per year in block rewards.
If you have 100% (~9TH) of the hashing power you get 2628000 * 100% = ~2,628,000 BTC per year.
If you have 10% (~900GH) of the hashing power you get 2628000 * 10% = ~262,800 BTC per year.
If you have 1% (~90GH) of the hashing power you get 2628000 * 1% = ~26,280 BTC per year.
If you have 0.1% (~9GH) of the hashing power you get 2628000 * 0.1% = ~2,628 BTC per year.
How you get it (p2pool, solo mining, paid per share, traditional shared pool PPLNS, etc) doesn't matter.