Taking a quick glance through http://www.bitcoincharts.com/bitcoin/ it seems the issue is that the 50 BTC gained from the block gets distributed to the miners like this:

1. Pay x BTC to miner 1, 50-x comes back to a pool account.
2. With the change from the payout to miner 1, pay miner 2
3. With the change from miner 2, pay miner 3
4. etc.

So depending on where you are in that chain it could be awhile before all of transactions before you have cleared so that your transaction can clear.

Maybe I am interpreting the information at http://www.bitcoincharts.com/bitcoin/ wrong though?

Isn't it possible to take the 50 BTC and send it to all the miners in one transaction? Then everyone would clear at the same time and there wouldn't be 90 transactions every time the pool solves a block.