Instapundit notes a paper on "link rot" which describes the ending of links in Supreme Court opinions, articles (and even blogs!).
Yes, it is annoying. Early on in thie blog (especially in the early GeoCities version), I'd often just link to an article and if it later died, the context was lost.
I reacted eventually by trying to quote from anything I linked to if if wasn't my own post, so if the link died you'd at least have the gist of the piece (and the link could give you source and date to look for the original if you really needed it).
Sometimes I still just link to an article if the hyper-link address describes the article sufficiently to get the point of the link (e.g., sarah_michelle_gellar_or_zooey_deschanel_why_choose?.com).
There are groups trying to save links (including saving links at the time of citation to guard against link evolution--which I exploited here), and I'd be remiss if I didn't note one group that saves an old GeoCities link to my Iran-Iraq War (First Gulf War) summary.
Sadly, this group--Webcitation.org--is in need of donations to continue.