I know that closed questions are the kinds of questions that are not good material for the site. For that reason, I don't think they should be advertised on the front page of the site (i.e. the newest feed, the activity feed, etc). I think that this could be damaging towards the site, because they will be the first things that first time visitors see upon visiting the site (and said visitors may not know what closed means, or even notice it). I think that a site will benefit from only the on-topic content being shown at the top of the feed, as it immediately defines what the site is all about.
So what I propose is this: Put all closed questions at the very bottom of every feed. That is to say, at the very last pages, not the bottom of each page.
Now I know that this may have some potentially bad side effects. For example, we'd be suppressing questions that are acceptable content for the site, but are just exact duplicates. Duplicates can serve as signposts for the original question, and can actually be useful as there are several ways to ask a question. For this, I propose that closed questions should still show up as search results. This way users will have no difficulty finding questions that are closed as duplicates.
Another potential side effect is that closed questions can be improved and re-opened. For this, I propose that this rule of putting all closed questions at the bottom be omitted for users with a certain rep amount (perhaps if they have enough rep to edit).
If anyone has any ideas on how this idea can be improved, or if you just flat out disagree with it, please share your thoughts.