I assume there is no validation required to prove you own the domain you are selling?

Example: http://i.imgur.com/VHd5uVg.png

Doesn't appear so.

It is also missing any system for aiding in the transfer of domains (it leaves this up to users to negotiate individually, which could introduce fraud). An escrow system would be nice.

Use Escrow.com. And this is a recently released project with many improvements coming soon.

You do have the ability to verify your domain. Perhaps in the near future, you won't be able to list domains that aren't verified.

This is great! I added some of my domains here: http://namebox.io/bluetidepro

Interesting! An option for filter by domain would be useful.