Hello everyone, this is my first post out of the newbies section!
Welcome 
So, which is the particular characteristic of Bitcoin, so different from the current physical moneys the society uses will make it fail in the long term?
- Selfish people in power (NOT all powerful people), create resistance. Bitcoin is most susceptible to social attacks.
- The arms race of security between cracking Bitcoin and securing it. I've heard this mentioned little on the forums. It can be enhanced with stronger algorithms, but every single digital device has the potential to be cracked/hacked, contrary to what you may think. There are known vulnerabilities to Bitcoin.
- Unknown social reason
- Disruptive technologies that may may pose a threat/opportunity to Bitcoin.
etc.
Basic two categories are social and technical, with many scenarios in each one.
I am very eager to see Bitcoin succeed, however, for that, all issues should get attention.
I do believe that Bitcoin is very secure, robust and sound, but I'm simply stating there are those that seek to dismantle it. It may be an easy race, but its a race non-the-less.
The last point of disruptive technologies could be a big one, however, we can't see the future.
Failing to solve all social and political problems and provide enduring world peace?
Out of scope.