It seems as though common courtesy, much like common sense, is not so common.
I was going to write a post detailing the latest story of how a blogger friend broke a story, only to have it "liberated" by another organization or media outlet without attribution. It's very annoying, and people who blog (as their second or third occupation, or as a "free" treat while earning money doing the day time doing other things) are expected just to put up with the constant mining of their blogs for stories by more mainstream organizations and journalists/editors.
When another author's work is cited in print, the original work is cited and noted in order to properly attribute the origin of the idea and to properly tend to any possible perception of plagiarism. In cyberspace, it is harder to prove the origins of a story idea, or to pinpoint its genesis, though patterns do emerge.
There is really no reason for a paid professional, journalist or otherwise, not to give credit to a blogger unless they are completely insecure about their own innate ability to generate original content.
Blog traffic can be a mutually beneficial and even profitable loop.
Bloggers whose stories attract large followings can aspire to paid positions with established companies, write books, get regular paid freelance gigs for themselves, or may start to earn a living delivering a written product that readers enjoy while larger outlets can simultaneously continue to develop their own branding and personality-driven columnist followings.
That a mainstream outlet keeps it pulse firmly on what is hot and trending in cyberspace is a testimony to its hipness, and shows it is staying current. Knowing where the best and freshest stories are is a good thing for traditional media.
It is common courtesy to attribute.
There is no shame in admitting that someone else's work has inspired you.
There is only shame in running with someone else's idea, or work and claiming it as one's own.
Fortunately for most bloggers/writers, ideas are a dime a dozen.
Stories can be "borrowed" or "liberated" rather than properly attributed, but what really counts is who generates them.
Bottom line: A writer's creativity can be linked, "borrowed" or plagiarised but never replicated.