I don't know what happened to the /r/worldnews post, but that subreddit's rules do say that it's for non-US sources and news. Also, that post linked to a Gawker site, which for many is reason enough to kill it.

Now trending from a more valid source:

http://www.reddit.com/r/worldnews/comments/1cerrp/boston_mar...

During disasters such as this, I appreciate reddit's scale (and diversity) for up-to-date information in the comments.

Seems that some other, far better source, should have replaced it by now. There were a few up-in-coming, but they too vanished.

I think its because the threads are getting too much traffic. It seems like reddit first will make a thread read only then will remove it from the front page, this all seems temporary. This is all from observation though Im not sure the actual algorithms involved here.

That's because the mods keep removing it -- reddit will have some contract with telegraph.uk or other such websites (they pay reddit for the higher traffic)