I'm not saying that you shouldn't architect that way, I'm just giving reasons why you might not.
>semi-determinate, constrained by the user's patience and willingness to upgrade
The user can vaguely determine it, but you can't. You can't guarantee a user experience without relying on the user not to be viewing your page on a two year old cellphone that they're simultaneously listening to music on and running three other js-heavy pages.
>the number of users the server must support is similarly semi-determinant, constrained by the popularity of the service, size of data a user could want to manipulate, and the desired speed of those manipulations.
You can assign whatever arbitrary amount of resources you want to your site on the server side, and allow in whatever limited (or unlimited) number of clients/visitors that you want to, so it's completely deterministic. The amount or resources utilized (whether on the client or on the server) will likely not be very deterministic, but you can have algorithmic problems whether on a thick client, on a backend data server, or on a backend presentation server.
>semi-determinate, constrained by the user's patience and willingness to upgrade
The user can vaguely determine it, but you can't. You can't guarantee a user experience without relying on the user not to be viewing your page on a two year old cellphone that they're simultaneously listening to music on and running three other js-heavy pages.
>the number of users the server must support is similarly semi-determinant, constrained by the popularity of the service, size of data a user could want to manipulate, and the desired speed of those manipulations.
You can assign whatever arbitrary amount of resources you want to your site on the server side, and allow in whatever limited (or unlimited) number of clients/visitors that you want to, so it's completely deterministic. The amount or resources utilized (whether on the client or on the server) will likely not be very deterministic, but you can have algorithmic problems whether on a thick client, on a backend data server, or on a backend presentation server.