Lately I've seen several websites with large ASCII art headers in their HTML. I don't get the point and it seems like this must just be a fad. For instance, tumblr.com has it:
<!--
. .o8 oooo
.o8 "888 `888
.o888oo oooo oooo ooo. .oo. .oo. 888oooo. 888 oooo d8b
888 `888 `888 `888P"Y88bP"Y88b d88' `88b 888 `888""8P
888 888 888 888 888 888 888 888 888 888
888 . 888 888 888 888 888 888 888 888 888 .o.
"888" `V88V"V8P' o888o o888o o888o `Y8bod8P' o888o d888b Y8P
-->
Adding this art to the file increases the size of each HTML download, which could equate to actual bandwidth cost increases on popular sites. I can't imagine why someone would do this on purpose unless they are just trying to be hip and cool and don't care about the extra bandwidth.
Is there a valid business reason for doing this? Is it a branding technique? Is it used to deter people from ripping off HTML and site designs?
Adding this art to the file increases the size of each HTML download, which could equate to actual bandwidth cost increases on popular sites.
You already answered your own question. It is Art! It is not supposed (or at least, it is not required) to have mundane functional value. :)
Seriously: as far I know, it has zero technical justification. It's all about decoration, and an insider's way of leaving a mark (after all, most people are not going to look into the markup). It's also fine: In times where DSL speeds are the norm in many target markets, the "bandwidth" argument is mostly a weak one. Every family photo you download weighs dozens, hundreds or thousands of times more.
The only useful use of ASCII art in HTML that I know of is using it as padding for 404 pages to prevent some browsers from showing their standard error page.