... and the same questions are asked over and over and over again. The forum has a rather simple, yet sufficient "Search this thread" function, which is apparently not used much.
To be honest, most often I don't think that's an excuse for anything at all. My reasons are different that you may expect though.
The VAST majority of forums and web sites have search functionality that rivals trying to find that penny you swallowed when you were five, over at the local sewage treatment plant. i.e Far beyond useless and well into idiotic.
I cannot count the number of times I've tried to search some forums or a web site and gotten a massive result set shipped in by a garbage truck, and not 1 clue as to how in any reality any of the results could possibly be considered relevant.
Now, different forums/sites have better/worse search functionality, but with so many bad search engines out there, people are basically trained to not search at a site.
It's a bad situation -- time and time again people get no useful results from searches, then get banged over the head for "not searching".
Google, Bing and Yahoo make the problem even worse as they set the bar so high for what people expect when they search.
Now, SMF forums actually have decent search as does vBulletin and some others. But they don't measure up to Google.
I've found myself going to Google to search like this:
some set of keywords site:somesite.com inurl:forum
But then I'm at the mercy of Google's index.
For newbies, I can see why they don't search. Still, there's no excuse for people who should know better, and developer forums... sigh... yeah... no excuse.
On a semi-related topic -- I sometimes start a thread when I already know of previous ones simply due to new information possibly being available. The older, the more likely I am to start a thread.