I've started recording ip's on my block tracker site. Currently connected to 600 nodes but don't want to increase the limit any further as bitcoind cpu usages gets too high.

http://pi.uk.com/bitcoin/unconfirmed-transactions

It will be interesting to to see whether any of these ip's are actually the transaction sender. A lot of them link to personal home pages and stuff.

When i collect enough data i'll use the frequencies of ip's associated with a given address to try and guess the owner.