CNN, WJS, Today, and ESPN have their own in-house team of developers and designers. i think that's not a good example.

Having a link to your website from a client website as you say yes is a good advertising as a web developer agency or hosting company. they are outsourcing services which means to them less head ache and saving money because they don't have to buy a server or have a full time in-house developer and SEO specialist which from my point will be a fair trade of having the companies link on their website as well as sometimes the agencies put their clients links on their websites as success stories or current customers.