It has happened many times that I got a thought, one which I deemed non-trivial, and I checked on the Internet, only to find that someone, somewhere had already either penned that thought, or had executed it.
Disappointment. But also an assurance, that my train of thought moves in the right direction.
This happened most recently on 19-Sep-10. I woke up in the morning, and had a thought that Microsoft should tie-up with Facebook to gain access to the valuable Like data building-up in Facebook's databases. Such a move would not only provide Bing with a few days worth of free marketing and elevate the perception of Bing among users' minds, but would also potentially make material improvements - both perceptual and real - to Bing's search results.
I queried on Google, and to my disappointment (and assurance, as said before), there were very recent news stories talking exactly this. Despite implied claims by Ballmer and Microsoft's executives that the relevance of Bing's results is at least as good and perhaps better than Google's, my first-hand experience is that Bing has a long, long way to go before its results start feeling as relevant as Google's results are today (and Google would've become even better by then).