It would apply ONLY within the scope of the DOCUMENT. Don’t look at it as in a ‘single view’ because it doesn’t apply to views, it applies to the XHTML DOCUMENT that is being OUTPUT by the application.
<html>
<head>
<base href="somebaseurl" />
</head>
<body>
<a href="--base--/whatever/url">link</a>
</body>
</html>
In other words, anything between the start and end HTML tags will be affected by the <base> element. If you have another view that is outputting a completely different XHTML document to the browser you would have to define another <base> element (or not if you don’t want it).
[EDIT]
Anything inside the <head> element will not be affected by <base>, only elements within the <body> element can be affected - but, the scope is still within the document since you can only have one <body> element per <html> root element.
