My first job out of college was a programmer for a company that made multimedia CD-ROMs. They would travel around the country to industry conferences for various professions, record the presentations, and put the recordings and associated PowerPoints onto a CD-ROM.
My boss (the owner of the company) had a great idea that our software could have a "sync to PDA" button that you could just click and it would send the presentations and audio to your PDA for on-the-go listening.
Now, this doesn't seem so impossible, but at the time, MP3 players had just come out, iPods were brand new, not widely adapted, and still prohibitively expensive, and the iPhone was still years away.
He didn't understand that there is a wide variety of PDAs out there and there is no possible way we could get drivers and specs for them all so that we could just zap everything over to a PDA. Plus, even if we could have solved the software/hardware issue (we couldn't), most PDAs at the time maxed out at about 64 MB of memory. In other words, a whole week or weekend's worth of recorded speeches and PowerPoint slides would NEVER fit. We'd be lucky to get a couple minutes.
I told my boss this, and his response was "well, I need you to try anyway, since I already told the customer we could do it."
So I tried, and needless to say, I was unsuccessful.