Track RSS ?

Has anyone come up with a way of either tracking their RSS feed, or asking would-be subscribers to register in some way before getting access to the correct url ?
I know that with many newsreaders they will auto-discover the feed, but can this be altered ?
I ask because I just checked my server log, after reading around this subject and realising it was way over my head, and I must have about 20 feeds going out, but I only know about 3 (friend’s IP’s).
For me it’s not a bandwidth issue – though it could be for some – and I am wondering just *who* is so interested in my ramblings.
With the feed being so ‘open access’ are search bots automatically snapping these up ?
Is there a way to hide the feed and only let somone subscribe should they leave their name / email ?
Is there another way to find out, other than server logs, who is taking the feed ?
I’m not expecting a quick hack by the way (though that would be lovely!), I guess it’s more of a discussion thing ….