So, the sermon concluded, you don't need a linking agreement. That's not the way the Web works. Don't get me wrong, there are some notable exceptions to this rule, such as when the linking company, intentionally or accidentally, leads users to believe that another business' content is really its own. A lot of these cases arise when third-party content is presented inside the referring site's frame, complete with the referring site's URL, corporate logos, branding, and even its advertising. The cases have pretty much shaken out the way you might expect.
Users benefit either way.
Linking is encouraged and allowed, until it becomes deceptive and confuses users. Historically, you haven't needed permission to link to anything, unless you were approaching the edge of deception or misappropriation. A very small minority of the more cautious companies, like my friend's, may have had linking agreements in place with every site to which they sent users, but that was probably rare. The lack of friction in building the Web is certainly one of the reasons it has prospered. But there's a new problem that could change some of these rules.