Many large corporation's "free helpful features" are aimed at tracking users. You see, every time one loads a web page, web app or userscript containing a favicon request to one of these companies, your IP address, the page you are visiting & and other information is gained from your device. This is used to help these entities build data dossiers on you, which can be used for various functions within the company, or the data can be sold on to data brokers from where it can be used with data gained from other sources to learn more about you than you know yourself. This data package can (and most likely will) then be sold on to marketing agencies, insurance companies, the government and any other entity wishing to learn about your lifestyle.

As a demonstration, this page uses the get.php script to retrieve favicons of the following well known websites.
The first time a favicon is called for, the script retrieves the favicon from a Google service, downloads, saves them here in the favicon cache & serves them to the requestor (from novarata.net).
When the same favicon is requested later, the favicon is accessed from this favicon cache and served.
Favicons are 16x16 PNG files, which may be easily upscaled to 32 pixels.
Examples of usage:
<ul> <li><img src="get.php?g=google.com" alt="icon"/>google.com</li> <li><img src="get.php?g=github.com" alt="icon"/>github.com</li> <li><img src="get.php?g=example.com" alt="icon"/>example.com</li> </ul>
It also works with subdomains and with complete URLs:
Alternatively, you can use CSS-backgrounds and data-* attributes used with JavaScript:
<ul> <li data-domain="wikipedia.org">wikipedia.org</li> <li data-domain="plus.google.com">plus.google.com</li> <li data-domain="lehollandaisvolant.net">lehollandaisvolant.net</li> </ul>
ul > li[data-domain] {
padding-left: 25px;
background: no-repeat 5px center;
}
var list = document.querySelectorAll("li[data-domain]");
for (var i = 0, len=list.length; i < len; i++) {
list[i].style.backgroundImage="url('" + "get.php?g="+ list[i].getAttribute('data-domain') + "')";
}