user1151: Similar to BitTorrent trackers. Or are all peers equal in ability and importance? 

user153: There is a node that will relay all transactions, regardless of whether a fee is paid:

http://en.bitcoin.it/wiki/Free_transaction_relay_policy

There are well-connected nodes that are recommended for use by merchants to avoid risk to a race attack.  Some of them have inbound connection whitelists so as to lessen the risk of intentional address list poisoning.

1151: <p>Similar to BitTorrent trackers. Or are all peers equal in ability and importance? </p>
 153: <p>There is a node that will relay all transactions, regardless of whether a fee is paid:</p>

<ul>
<li><a href="http://en.bitcoin.it/wiki/Free_transaction_relay_policy" rel="nofollow">http://en.bitcoin.it/wiki/Free_transaction_relay_policy</a></li>
</ul>

<p>There are well-connected nodes that are recommended for use by merchants to avoid risk to a race attack.  Some of them have inbound connection whitelists so as to lessen the risk of intentional address list poisoning.</p>
