Having a few consistent semi-reasonable examples might be nice (but then I don't know the full plan for the docs, so feel free to ignore).

That is, `~Point` is never useful^, but a linked list is sometimes useful; and it's amenable to introducing owned data, patterns, generics, borrowing/references & lifetimes, traits, shared ownership (e.g. a `enum List<T> { Nil, Cons(T, Rc<List<T>>) }`), and even, at a stretch, shared memory for concurrency (the same thing but with `Arc` instead of `Rc`).

(One can also discuss runtime representations by comparing that `enum` definition to a definition like
```rust
struct List<T> {
     data: T, next: Option<~List<T>>
} 
```
(assuming that these do end up being represented differently; would have to check).)

(^it's useful for creating `~Trait` objects out of a `~Point` but that's pretty much it.)