Wow, you will get a lot of this - I can see from your rating that this is a bit new for you.  I know it's not fair, but as another poster said, EBay really seem to protect the buyer, that's just the way it is and no amount of getting annoyed will change it.  It's not fair I know but they will never change it.  You will feel like you are banging your head on a brick wall, but it will happen - all you can do is if they don't pay, open an unpaid item dispute, then if they still don't pay, put them on your blocked bidders list and move on.  Eventually if they keep doing the same they won;t be able to buy anymore on EBay anyhow.  A lot of sellers here (me included) have our settings set up that people with 2 or more unpaid item disputes in the last 12 months are blocked from buying anything from you.  You should check your settings and make sure yours are set up like this too.