People that back out of knife deals should be blacklisted by all makers, custom or otherwise.
If you can't keep your word, you shouldn't order a knife. It's that simple.
Todd, you should let them know they have a week to respond to the original emails, or you're selling the knives.
You might indicate that your knives are in demand, and you cannot hold knives for people who do not communicate or who do not pay their bills.
My two cents anyway.
Just to add...
As for the folks who backed out? I would let them know (politely) that they should not bother ordering another knife without paying in full up front.
as well... i think Todd should give me a cyber tuesday deal

heh, i mean:
it's esp ironic in some maker/buyer interactions where someone begs you to make or sell something, get a special deal, or rate, or something... and then backs out, doesn't say why...
then you find out they just dropped all of "your money" on something else, or many other things - they HAVE the money. they just didn't do anything about it. gah.
but wait, they come knocking again. guess what? they're likely to flake out. again.
simple rule i have from many craftspeople: for things that someone needs to reserve, but are not special, easy to sell: they don't have to necessarily deposit, but they have to be ready to pay on DATE... otherwise, the deposit is up front, modest, but seriously enough, non-refundable, and if anything EXTRA (rare wood, special steel), they pay up front for that too so materials can be purchased now, not later ... for the maker, they REALLY should buy the materials at the cost stated - there are a few guys that wait and wait, then say to the buyer "oh, sorry, but in the last 3-4 weeks cocacolawood went up 50%, and i already spent your deposit, so, you know, need more money (and repeat: oh, those bolsters had to be machined by hand, took twice as long, more $$$) - no. that's the maker's problem... the price is the price is the price...
bottom line: make a deal, both sides stick to it. on time payments. on time delivery. no surprises!
public shaming is good too. hopefully, no Beckerhead engages in antics. remember: your good standing is required!