Tech Products Ahead of Their Time
mashable.com
mashable.com
A lot of these failures weren't hinged on the lack of some technology, it's just plain bad execution.
See: N-Gage. There was nothing preventing them from building a perfectly viable handheld game console that was also a phone. It was just horrifically engineered. Same story goes for the ROKR - it was not all technologically infeasible to create a phone tightly integrated with iTunes and music playing... but they just sucked at it.
There are a lot of times where I think, gosh Google Wave would have been great for this situation or that situation. Too bad they killed it before it found an audience.
P.S. Sigh... can't stand the pagination on mashable articles.