I think host tracking of logs is a brilliant idea... however there would be problems when it comes to different users with the same host mask for those of us not lucky enough to have static IP's ;p
you would need a popup whenever someone with the same host mask messages you to ask if it is the same person, otherwise you would end up with one log file and multiple people. and i, like many people, hate popups ;p especially when you're in the middle of typing something, and the popup pops up right when you're about to press enter and it screws up the settings ;p
perhaps a manual exclusion list could be included, but this defeats the purpose as it would take just as long to merge the log files as it would to enter an exclusion :P plus if they have the same host, the exclusion would have to be done via nick, and this is extremely messy. plus the exclusion could only be done when it is too late, and someone different messages you and makes it into the log file.