also withholding blocks, to manipulate the perceived hashrate and effectively attack other mining pools, is a problem
The block withholding attack might actually end up being what limits the size of pools in the end.
If it's no longer safe to accept random members of the public into a pool, then the pool membership needs to be limited to trusted hashers.
This means a larger number of pools for a given number of hashers.
I used to really like small pools, until the hashrate started going nuts.
when your profits are being cut by 30-40 percent every couple weeks (every 10 days sometimes) it's hard to stay at a small pool that is having a "dry spell"
having said that,
305673 5 minutes 150 638.12 BTC BTC Guild 86.09
305672 8 minutes 193 204.05 BTC Discus Fish 115.96
305671 10 minutes 351 477.82 BTC BTC Guild 202.79
305670 22 minutes 394 973.33 BTC GHash.IO 193.73
305669 32 minutes 447 1,595.25 BTC GHash.IO 290.72
305668 42 minutes 111 798.10 BTC GHash.IO 91.57
woohoo! btc guild! stuff it in their stupid ghash faces!