Why doesn't Twitter and Google API documentation encode ampersands in URLs?

Question

I have read I should encode my ampersands as & in HTML.
However numerous code samples from respected companies somehow forget to do this.

Just a few examples off the top of my head:

Google Web Fonts sample code:

<link href='http://fonts.googleapis.com/css?family=PT+Sans&subset=latin,cyrillic' rel='stylesheet' type='text/css'>

Google Maps documentation:

<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false&language=ja">

Twitter Anywhere official tutorial:

<script src="http://platform.twitter.com/anywhere.js?id=YOUR_API_KEY&v=1" type="text/javascript"></script>

Is there any real benefit from not escaping ampersand in links?
Is this related to browser quirks? Is this just a mistake in documentation?

Dear answerers, please make sure you're answering the right question.

I know I should escape ampersands per spec. I also know why the mechanism was invented in the first place. I'm not asking about this. My question is:

Is there a reason API documentation by respectable companies often violates this rule?

Answer 1

Two different contexts here.

1. Within the context of a javascript href, the & is just fine and should not be encoded.
2. In an HTML link the & is forbidden and should be escaped.

In the HTML link context an HTML character entity will be decoded before the address is passed to the HTTP process; a URL-encoded character will not, as the server can read it directly.