When your company can't keep the interesting people any more
If you've worked in a suitably shiny company, you may have had this experience. You'll be digging around through interesting things online, and you'll come across something that really catches your eye. Maybe it's a particularly good dissection of some fundamental part of your operating system. It could be a brilliant way of looking at a problem, or it could just be a web site which fills a need quite well.
In learning more about your discovery, you also get some information about the person who wrote it or built it. You dig around and find some other work by them and it's also good solid stuff. This makes you happy.
Then, some time later, you'll be reading some random bit of mail at work, and you'll see a name go by which seems familiar. It might not "click" at first, but eventually you realize you somehow know that name from your non-work exploration. What is that name doing on your radar here at work? Did they somehow manage to mail an internal group alias from the outside world?
You look a little more closely and then realize they have a company e-mail address, and in fact have now been employed there for a short while. They showed up at some point and you're just now finding out about it. You chalk this up as a sign that things are moving in the right direction and go about your business.
Remember that web page about making the tiniest ELF binary possible? It used all sorts of nefarious tricks to get things squished down tightly. The author has a fairly unique username, and I was quite pleased when I found it internally, and it was in fact the same person. That's the kind of person you want to have around because they obviously know their binary formats.
At some point you start running searches against the employee directory to see if certain people are already working there. It beats waiting for that random chance of a mail from them crossing your path. You discover more who have been lurking within, and smile, since this can only mean good things.
Then, some day down the road, maybe you're showing off an internal site to a relatively new employee, and you decide to bring up the "who" page for one of these notable individuals. That's when you get a nice 404 page not found or some other error which makes it clear: that account does not exist.
You run a quick query against the internal systems (LDAP or whatever) and discover that yes, they were in fact an employee for a while, but they are gone now. You chalk this up to bad luck and show the new person your own page instead. They appreciate the help and move on.
In my case, the smallest-ELF-binary author person just poofed one day. I went to look for his entry in there and he was gone.
More time passes, and you keep noticing it. People who were just there before keep vanishing. Some problem comes up and you think you will just contact so and so, because she was so good at something similar, and she actually works here! Then you go to ping her and discover it's a dead end. She's moved on, too.
At some point, enough key people have disappeared, and the company is not just the same place any more. This is when you should ask yourself why you're still there. Maybe you like watching train wrecks, and there is something to be said for the experience of witnessing a truly epic crash.
I am reminded of the story about a weekly bridge game at Netscape as chronicled in chapter 8 of Being Geek. There's one line in particular which I found chilling:
They noticed when one of those who had humbly done the work that defined the company no longer believed enough to stay.
I've now seen it myself, and it isn't pretty.