It's growing very fast in 1st world countries, because they have the infrastructure to support it. {ATM installations, fast and reliable and cheap Bandwidth, to host eCommerce sites, that supports
BTCIn 3rd world countries, where it is needed the most, for it's cheaper and fast micro transaction, it's growing slowly, due to the challenges, I mentioned above.
Once the 3rd world countries gain access to this, it will explode.