I also notice this forum doesn't include info on Qnas hardware . Is there any reason for this?
No particular reason. It just happened to be. There are already good Qnap forums outside, that reduces the need. (BTW, there is a Qnap wiki, http://qnap.nas-central.org
, but it's barely maintained).
What is it about Samba that makes it inappropriate to use over the web?
It's not designed for WAN use, which makes it vulnerable. Many ISP's block the default samba ports for that reason.