Hello 'zen-way',
Of course ebay supports you with deadbeat buyers. But to get your fees back you have to file an Unpaid Item case. No one can help you if you do nothing. Here is a link telling about that:
http://pages.ebay.ca/help/sell/unpaid-items.html
Recent changes enable you to file an Unpaid Item case after only 2 days, - instead of the 4 which the link still says.
I am assuming, however, that you have sent your buyer a friendly reminder about payment, and are not sitting back silently like a couger waiting to strike, and spring an Unpaid case on someone who may have genuinely forgot.
Something else you can do to help yourself is to block people with 2 or more unpaid items. They tend to be repeat offenders, so you can do that here:
http://pages.ebay.ca/help/sell/manage_bidders_ov.html#set
If you are overwhelmed with non-paying zero-feedback newbies you may wish to block non-paypal account holders, but that will not 'solve' the non-payer problem because plenty of kids with paypal accounts have zero sense of fiscal responsibility. Instead you would be blocking all that credit card revenue, - which is why very few sellers actually do that.
As one person aptly pointed out here a while back, - if you block too much you end up listing your unsold items over and over again.
If, on the other hand, non-payers are making you apoplectic it is probably best for you to consider setting all your items to 'Buy it Now' with Immediate Payment Required. That way you don't have to block anybody at all, - and so maximize your income potential whilst completely eliminating non-payers. Here is a link to tell you all about that:
http://pages.ebay.ca/help/pay/require-immediate-payment.html
I wish you well with it. 
Oh, I meant to add that you cannot leave a negative. Sellers cannot leave negatives for buyers. They want to, oooooh how they want to. And in a way it's a shame they can't because that way we could readily discern who the snarly hot-heads are.
Therefore, - would you really want all those whiny negatives as a permanent record of your outgoing feedback for all your 'good' buyers to see? Moreover, if you could leave feedback for those transactions, so could your non-buyers. Imagine how some of them might respond to those negs you leave. Imagine what they might leave for you.
Naah, it's probably better to just file those Unpaid cases, get your fees back, block those who don't pay and block all non-payers, list with Immediate Payment, - and that way you always get paid and will look like someone wonderful.
