As early as grade school, we’re told to list our sources at the end of book reports. In journalism school, you’re taught how to find, cultivate and protect sources.
Many writers on the Internet aren’t great at listing their sources, though.
I follow mostly the same guidelines as Stephen. The only issue I come up with is when I open a link to read later and forget who linked to it, but that’s an honest mistake.
Guys like Jim Dalrymple have made a career linking to and helping others. The goodwill it builds is long lasting. There’s absolutely no reason why you shouldn’t attribute sources.
I like how Patrick Rhone put it: I like to think of them as “Breadcrumbs to the truth”.