AJAX: server side JavaScript

I just found this post with a very interesting idea: code does not need to exist on the client beyond connection scripts; JavaScript can be sent to browser to be executed; basically, remote invoking via passing of code (aka using eval with JavaScript received from the result handler)

Just like everything else, it has its pro's and con's, but overall, I think that in a security and even lazy loading standpoint this is a great idea.

I guess it really depends if you are using AJAX as an add-on for a web application, or to build a full application. In a robust application, the 'init' call will load all those JS components that need to be persistent and leave them on memory, and all the rest of the calls can only transfer and load the needed JavaScript, thus optimizing initial loading time.

What do you think?