And in the age of Google, where you can just put quotes around the first sentence and find the original source, it shows a complete lack of care.
On a more serious note: it would be interesting to add a check to CMS systems to automatically look up all sentences in an article before submitting and apply information theory to compute a "plagiarism" coefficient. No doubt these kind of systems already exist to detect student plagiarism.
If one of those software producers would provide an API (something similar to Automattic's Akismet for spam) I'm sure there's money to be made in selling that service outside the academic realm.
It's pretty nice actually, can recognise when things are quoted and not passed off as your own.