Interesting idea. Well put it on the list of things I should try some day.

After a quick look at the site, I like the idea. But I wonder where it's limitations start to get in the way.

How about security, if I can modify the page, who else can? And who controls that?

How much code and logic does it handle before getting difficult to maintain? And how much data?

If I make an useful app with it, say to track beers, can I share the app with other people without so they can track their own beers, without sharing my personal data?