According to "a team of statistical physicists" – and that sure sounds official, doesn't it? – barely anyone reads stories on the Internet more than 36 hours after they are posted. The story from physicsweb that explains all this is complicated – apparently, "the number of people who read news stories on the web decays with time in a power law, and not exponentially as commonly thought." But the basic point is pretty simple, and it speaks to the value of e-mail news alerts as a way of keeping people from missing significant news.
I do feel compelled to point out that I came across this story for the first time today, even though it was published four days ago, via the excellent aggregator greenslade. But it certainly seems true that the Internet has put so much information at our fingertips that it's rare that people pay much attention to anything that feels even the slightest bit old.