After seeing the third "Urban to Browns" thread in 24 hours, I had two possible ideas.

1 - typing a thread title brings up other titles from similar threads. I know EliteFTS has something similar in their Q&A section. Pick a topic, ask a question (though the order is backwards) and it will give you suggestions to other similar questions. (http://www.elitefts.com/q2a/?qa=ask). So someone writes Urban and Cleveland and all similar threads pop up, including ones about him at Cavs games or him recruiting at St Benedictine (Cleveland).

2 - dupe reporter like helmet stickers. Just have a button or link reporting dupe, get 10 reports, the thread is frozen or deleted.

edit: And just to be clear, part of the reason might be because the previous threads have been deleted completely so they obviously won't come up even if the dupe poster searched for the thread