depending on how much the item is worth, i.e. 
what you paid (usually your reserve price) or at 
the very least what your minimium was IF the item 
is valuable i.e. a rare cel, it might be worth 
your while to have ebay help you investigate the 
situation by filing a claim. Please note that 
there is a charge for this service AND the item 
has to be worth x amount of dollars. There is 
tons of verbage on this at ebay's help section. 
If the item is too low in value, speaking from 
the many experiences I've personally had on ebay 
and yahoo auctions, leave them BAD feedback after 
14 days. Usually if repeated emails/requests for 
them to send payment/contact you fail to produce 
a response, screw 'em. Good luck and hope you can 
resolve the matter w/o further heartache. 
Deadbeat buyers & sellers suck!