Weird example of string interpolation in directives guide

In the [developer guide for directives](http://docs.angularjs.org/guide/directive), the string interpolation example is odd.

``` html
<img src="img/{{username}}.jpg">Hello {{username}}!</img>
```

I would expect:

``` html
<img src="img/{{username}}.jpg">
```

and/or:

``` html
<p>Hello {{username}}!</p>
```
