Hi there,
To reduce the % of -ve fbs set some restrictions for few type of buyers.
Like :
Buyers with Unpaid Item strikes.
Buyers with policy violation reports.
Buyers with a negative feedback score.
Buyers who may bid on several of your items and not pay for them.
Buyers who haven't gone through SMS verification.
You can do this from
My eBay >> Account >> Site Preferences >> Buyer requirements.
I agree that mostly seller suffer from these kinda of issues but at least we could take some steps to minimise the risk here.