There's a note at the bottom of the home page:

"The Bitcoin address and Bitcoin-to-email options are temporarily offline for system updates. These options should be back up on Monday, March 11. We apologize for any inconvenience and thank you for your patience while we run these upgrades."

Conceptual question: Do I contribute to the bitcoin network just by running the Bitcoin-Qt v0.8 client?

I understand that I'm not creating blocks. But does the client play any role in the peer-2-peer verification of transactions?

A Tx is supposedly trusted after "6 confirmations". Who does the confirming? What constitutes a confirmation? Is it simply when 6 additional blocks have been added to the block-chain?

When I first ran the client, I had to wait several hours for the block list to sync. Is it just that I got the block list from other clients,  and that's the "peer2peer" nature of the thing?

Aren't you also paying for that 32GB volume?