The first concern I had/have is about security. If everybody runs their own server, isn't this a security nightmare waiting to happen?
I understand from the presentation that these websites won't run php or other server side scripts which at least take some concern away.
Tara also showed how easy it was to copy a website, while pretty cool, that is also a nightmare scenario for most companies. If your competitors can clone your websites and pretend to be you, how do users know who's data they are looking at?
