From the Washington Post comes this sentence, which an exposition of interruption:

«The current room, built over Franklin Roosevelt’s swimming pool — which is still there — dates back to 1970, and over the years has been the scene of daily combat between press secretaries and reporters.»

I would not have wanted to have been the copy editor for that piece.
Note the double dashes, which are standing in for our old friend the em dash (—). This is probably due to the difficulty of typesetting on the web. Having working in a publishing environment, it is difficult to correctly typeset word processor docs to HTML. The problem isn’t actually technical, but human. It’s hard enough to get authors to produce anything, let alone correctly marked up manuscripts. The double dash is probably a hold over from the days of typewritters. Still, a small perl script could convert the double dash into an em dash easily enough.

On the matter of content, I don’t think this is a bad sentence. However, it might be a bit challenging for the average consumer of news prose. If asked, I would have suggested breaking the sentence in two, like this:

Dating back to the 1970s, the current room is built over Franklin Roosevelt’s swimming pool, which is still there. Over the years, the room has been the scene of daily combat between press secretaries and reporters.

Note the perilous use of “1970s.” Besides the hideous fashion memories invoked by the mention of this era, grammarians just can’t agree on how to properly spell numerical decades (or plural numbers, in general). Depending on the editorial traditional, you will see “1970s” or “1970’s.” I think you’ve just got a pick which version you prefer and prepare to be berated for your poor choice. It’s a lose-lose situation.

I can’t fully express to how much more delightful quibbling over grammar is to writing Java code. My non-technical friends will just have to trust me.