Is wandering off topic such a bad thing? I mean everything in this big planet is somehow connected, so isn't it likely that it's always going to happen one way or another? I mean unless it is eating up memory somehow, it's kind of interesting to watch where discussions can go!
It's all up to you dude! (;
Yes wandering of topic is a bad thing. It is useful for those who want to follow particular threads and not others to have them catagorized to some degree.
It also put some discipline on the posters so that they don't insert their own little pet ideas into all the theads.
It also helps stop some people from diverting attention from the fact that they don't actually have anything to say on the actual topic at hand or from trying to shift the goalposts.
Of course, there is a lot of extra things that come up because you are right when you say everything is connected. But that is easily handled by spinning off another focussed thread.