I have seen the exact same AP article under different titles around the world. Why is this? Are different news organizations doing this or does AP 'retitle and re-release' the same piece? This causes duplicate posts under different titles. Is there another way to cross-check this?
AP posts an article, other sources pick it up and change the title. IMO, they are the worst offenders. Then, posters here will faithfully search and post it, only to find out it's been posted 3-4 times already. The exact same article, different titles. If the articles are posted within 4 hours, we generally will link them. Our guideline is after 4 hours, we'll leave them up. A lot depends upon how often they were posted, how hot the topic is, how many posters are actively posting on the duplicate. It's not an exact science, and it's not set in stone. That's the dynamics of this place.
What I do (and I've avoided duplicates this way) is search for bits of body text on Google News. You'll find duplicates, even if the two titles are totally different verbally.
For example, looking with the phrase "Swiftboat Vets," I found a story entitled
"Swiftboat vets, Kerry supporters speak in Greenville"
After searching for the body phrase "Two men who served with John Kerry," I then found another story, entitled
"Vietnam vets back Kerry's bid"
Only one word is common to both titles (FR's search function treats "Kerry" and "Kerry's" as different), but the text that I skimmed was identical or nearly so.
This method, while not foolproof, is a start. And while there are valid reasons for changing titles, I don't care much for changing them around just for variation or whatever. :p
Oh, and thanks, moderators!