We don't do it for the advertising.
Every once in a while we notice someone come into that forum looking for hosting they can't afford. We take a look, and if it's a good cause then we'll offer them free hosting. The leading paragraph from one site we host for free states:
I'd never heard of Bartter's or Gitelman's Syndrome and apparently neither have a lot of people. The site was built as a resource center for others and there's a small community of people who's children suffer this syndrome. They meet and talk online. I'm the father of a very healthy 2 year old, and reading this website made me appreciate just how lucky I am. When there was a need for this site to stay online, we stepped up and offered them free hosting and support.
This website is dedicated to my daughter Charlotte. She has a rare kidney defect, Bartter's Syndrome that causes her to lose potassium and magnesium. If you are looking for more information on Bartter's or Gitelman's Syndrome, you will find it here.
Since then, two more sites were added to our servers that are related (one is paid for per month). As far as I can tell we're hosting the most information on this condition on the internet today - it's rarely known even amongst medical circles.
There's a link to us on both sites, but it's never been required, and I can't think of more than a handful of signups that may have eventuated from those sites. However, the off chance that come other parents may discover what their child has, and find ways to help them is reward enough for the small amount of resources the site uses. We host a few sites for free, but all are well worth the time and effort - which is minimal.
So why do we do it? As I said, it's not really for the free ads. We have the resources to be able to do it, and some people are trying very hard to keep their sites online when they can't afford monthly fees. Sometimes the right thing to do is reason enough
Former Webhost... now, just a guy.