I think one of the biggest barriers to entry right now is that business don't feel comfortable accepting a currency that's so volatile and which they can't cash out immediately. I'm a relative newcomer to bitcoin and own an online gaming business. We're looking into bitcoin adoption, but one of the trickiest things is how to to do pricing when the value of bitcoin is still tied to the USD. Until more places have stable bitcoin prices, merchants will be hesitant to set stable bitcoin prices.
A bit of chicken-and-egg, but there it is.
Yah there it is...volatile, might be unable to reuse it, and who goes first. All the obstacles in a nutshell.
I think there are parallel operations that go on to make any payment method gain traction: People working on making transactions as easy as possible (comparable to easy hand over cash transactions), and people willing to take a risk in accepting them before they are widely accepted. As the second grows, volatility reduces as prices have something other than $$ to peg to.