One of the world's large credit card networks processes on the order half a trillion dollars in a typical 30 day period. So bitcoin has a way to go yet before it's volume is significant compared to other ubiquitous electronic payment methods.
Consider that they need to grow by a great many orders of magnitude to become globally economically significant, yet consider that the supply of bitcoins is relatively fixed.
How smoothly do you think that is going to work?
If you believe in the future bitcoins, you also have to believe that their value will have to eventually sky rocket by several orders of magnitude. If you believe this you should hoard every bitcoin.
So if you actually believe in bitcoins, why would you ever spend one?
If you don't believe in bitcoins, why would you ever accept one?
do you see the problem yet?
Because you have to, and there is no other realistic or better choice.
As such, it's interesting to see when and how such situations arise.
"Bitcoin Seeks New Life in Africa: A digital currency without a central bank could be ideal for economies where the mobile phone is king but the banking systems are weak."
(This on a website for hackers and startups. Pfft.)