When is a CDATA section necessary within a script tag?

Question

Are CDATA tags ever necessary in script tags and if so when?

In other words, when and where is this:

Answer 1

CDATA indicates that the contents within are not XML.

Answer 2

That way older browser don't parse the Javascript code and the page doesn't break.

Backwards compatability. Gotta love it.

Answer 3

When browsers treat the markup as XML:

<script>
<![CDATA[
    ...code...
]]>
</script>

When browsers treat the markup as HTML:

<script>
    ...code...
</script>

When browsers treat the markup as HTML and you want your XHTML 1.0 markup (for example) to validate.

<script>
//<![CDATA[
    ...code...
//]]>
</script>