If people want to procrastinate, they're going to procrastinate anyway. They'll just do it on other websites -- and if anyone else is like me, they'll probably get sufficiently irritated by coming to a frequently-broken website that they'd end up coming here far less frequently. As for the notion of improving the feeling of community by having everybody turn up at once... do we REALLY want to get dozens of posts all…
Don't social news sites sort of depend on them being "up" in the background "working out" what is interesting? Won't bringing it down for 3 peak hours just reduce the churn of good material?
I tend to check hacker news/reddit/etc. at very specific times (like first thing in the AM, right before and after lunch, etc.). If it's down during those times, or if the content is stale (because it's spent the past 3 hours being down), I'm not going to get more work done. I'm going to just stop coming.