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.
Just to confirm my own code changes...Are you logging the ip from the 'inv' or the 'tx' message? I originally logged the 'tx', but realized that the 'inv' message comes first.