The first part—that bloggers borrow topics from each other—isn’t a new observation. Link commentary is one of the clasic forms of blogging, right up there with filling in quizzes and posting pictures of your cat. What’s worrying is the lack of attribution.
Attribution is a critical part of good blogging etiquette. It provides “discovery credit” to the blogger who directed you to something, but more importantly it acts as a tool for communication. It’s easy to tell when someone is linking to you, via referral logs or services such as Technorati. By attributing something to another blogger you make two useful statements: I read your blog (or at least stumbled across it somehow), and I’m interested in that particular entry. This is valuable feedback.
This still doesn’t help you if you clicked on a link in an aggregator such as NetNewsWire, but I’ve started habitually opening the real entry in a browser before clicking any links to ensure I maintain referral information. This is particularly important as the bookmarklet I use for updating my blogroll grabs the referrer for automatic “via” link generation.