Thanks for the feedback guys. It's nice to hear the opinions of our users because it helps to make the site a better place for everyone.

Here's my ten cents on the subject:
The default setting on the search page (search topic titles only) was a deliberate act on my part. As Hypnotist said, if you perform a search within the "topic title & text" you'll get a mass of results - too many to trawl through. Whereas searching just within topic titles gives a much more refined set of results. One of the forum rules is to use a descriptive topic title - this is to make it easier to search for an appropriate title. We as Admins/Mods keep an eye on topic titles and rename any that aren't very descriptive (e.g. we may change something like "A quick question" to "How do I edit the salary cap", etc.). Obviously some do slip through the net but we do tend to rename most non-descriptive topic titles.
Let's take three examples of duplicate threads that have recently been closed. I do this simply to show that using a topic title search is helpful - I don't mean to make an example of anyone:
1) A topic asking where all of the TBL 2007 Cards can be found. I searched "tbl 2007 cards" (without the speech marks) within topic titles only. It returned a massive 170 results (possibly because "tbl" and "2007" are mentioned in many topic titles). I wouldn't expect anyone to trawl through all of these threads, but the first result is the "
TBL 2007 Cards For NHL Players Now Available!" thread - that would be an appropriate thread to ask the question.
2) Changing the salary cap and what effects it has. A topic title search for "salary cap" (without the speech marks) returns 20 threads (as well as three locked duplicate threads). I can see from the list of results there are a couple of threads that it would be appropriate to ask the question.
3) How to retire jerseys. A topic title search for "retire jersey" (without the speech marks) returns 15 threads (as well as two locked duplicate threads). I can see from the list of results there are two threads that would be appropriate to ask the question.
In the instances that we have closed threads they have been on topics that I/we feel are easy to search for - we're not closing threads that are hard to look for. I think it's just that we've had a flurry of questions recently that have been answered before. As has been said before, we want to nip this in the bud in order to prevent it snow-balling into the sort of thing that goes on in the SI Forums (e.g. hundreds of threads on the same question, information becoming hard to find because there's too many threads on the same subject, etc.).
I think that the suggestion to have a search button on the New Topic page is a very good one. It can be easily done and I will do so when I have a spare half an hour to do so. I accept that the Search button is not immediately obvious at the top of the page in black nav bar - it's something that hadn't dawned on me before. I agree that that is probably a factor in people posting duplicate threads.
I really don't want to scare new users from posting questions - it's the last thing I want to do. We've always prided ourselves on having a welcoming and helpful community. I think that Hypnotist's suggestion of embedding a link to the appropriate thread is a very good one and will pass this on to the other Mods to ensure we do this from now on. To keep things tidy, we're going to delete the duplicate thread after about five or seven days. This will give the user time to see the link we've provided for the appropriate thread. Deleting the thread will keep the forums tidy and easier to browse.
Perhaps we as Mods should compile a large FAQ which lists common questions/subjects and links to the appropriate thread. We could then sticky these at the top of the forum.