I haven't had a problem with zfb bidders yet - one 
even overpayed via Paypal BEFORE any of the 
confirmation e-mails went out! ^_O

One thing I *can't stand* about evilBay is the 
ability for anyone to quickly acquire multiple 
ID's, and for bidders to acquire ID's without the 
kind of verification that sellers go through (cc). 

Anyway, you should be able to view the user ID 
history of an evilBay ID... I forget the exact 
page, but it's there...

I had this problem with a non-paying-bidder that 
had a relatively low rating (like 6 or something, 
half of which were negatives - ALWAYS CHECK THE 
ACTUAL COMMENTS IN ANYONE'S FB PROFILE!!!!!!!!), 
and I thought the e-mail looked familiar. I tried 
to do a little research on the forum, b/c I though 
I saw that e-mail there before. No luck. But I did 
some more digging on the bidder's e-mail host and 
asked the host provider to provide me with the 
bidder's personal information like REAL NAME - 
after explaining the situation. I recognised the 
person's name as someone who had been accused of 
being a really bad NPB and stalking a seller on 
the forum O_O, so I immediately contacted evilBay 
and they cancelled his account. *STILL* nothing 
like this would happen if the !@#$%* people at 
!@#$%* evilBay would require ID verification on 
bidders! I'm still a bit miffed. >_<

Anyway, how I handled my zfb bidders is simple - 
after the first confirmation sent by eBay, send 
your own message detailing the usual (shipping, 
total, etc.), with a simple warning and requisite 
reply ("please reply within 3 business days of 
this message with your SHIPPING ADDRESS"). If they 
don't reply to your first message, after the 3 biz 
days send another message reiterating your 
information and requisite reply (I often add 
"since the first message might not have reached 
you" just to be polite). This gives them about a 
week to contact you, which IMHO is quite enough. 
If they don't reply to your second message, I'd 
"request contact information" from eBay. Note that 
this sends you the name and phone number of the 
bidder and VICE VERSA (they get a message with 
your info, too). You can opt to call them by 
phone, if you want, I personally never do - the 
message serves as a kind of warning. After all 
this, no response, I'd file a NPB with eBay, or 
just drop a negative on the sucker.