Amusingly, I've had the opposite problem: I see some things, think they are the best ideas ever and then watch them fizzle away. Perhaps the largest example of this would be Wave. When I first heard about Google Wave, I was incredibly impressed and immediately signed up for the beta. I really did think it would replace email and IM--it was an elegant solution that did both, at the same time. I then played around with…
I mean:
1) Google Wave -- a confused mess of a mail/im/web/social offering that didn't exactly knew what it was and solved non problems.
2) Gnome 3 -- Gnome 2 had languished for years. Why would 3 change that, especially since most of the changes planned were incremental ho-hum stuff combined with arbitrary rewrites of core technologies sure to take them years to complete?
3) Zune. Nuff said.