Because of BTC inherent nature to encourage hoarding, perhaps the best overall solution to encourage spending in BTC is for merchants to offer discounts for customers who pay using BTC.
- Due to the way BTC increases in value, merchants can be almost sure to earn back the discount multiple times.
- Consumers are given more spending power because they have discounted goods and are encouraged to acquire and spend BTC.
I have already offered my building services in France for a discounted price and the reaction has been pretty positive. The client won because he got the work for 10% less than if he'd paid in fiat and I won because the BTC price has increased over the cost of the discount making it cash positive for me.
So maybe discounting goods and services in BTC based on BTC future value is what is needed to encourage spending.
bitcoin is so volatile, so if a vendor decided to accept them.. they could lose a lot of money. why put your business at that kind of a risk? they'd also need fiat to pay their bills and overhead.. so much of it would probably just be converted back into fiat, which means they sold at a discount just so they could convert it back to cash.