Why don't people ever answer or comment on the forum topics?And why do people look at them and not write anything?

a) they do but they dont show in updates so it takes a while
b) if they have nothing to say they read and leave..better than saying OMG I DUNNO!

For one thing, when a forum is added to a spot, it doesn't show in your updates. So basically you just have to happen upon it on the Spot page or actively check the forums for new stuff.
As to why people view and don't answer- I guess they just don't have anything to say.

I think the reason is that some forum topics are (to some people) just not worth commenting on. A perfect example is the forum topic that advertises a new spot, link, video, or something out of Fanpop.