Well look, there is a risk everywhere. I think that the credit card chargeback rate is about 20-25% and merchants take this risk on themselves. But you are also using a logic that person that paid $3 for a cup of coffee won't be doing a chargeback. It's not worth a risk.
We can use the same logic about the Bitcoin double spend. But if you are looking for a 100% solution, I guess that Bitcoin is not ready for paying a coffee like Ciyam has said above. Honestly I am not sure that this will be ever necessary in order for Bitcoin to succeed.
Mickeyb, you are thinking "western" here. The Philippines is not western. It is an under-developed third-world country. Less than 20% of adults (those 18yo and over) have a bank account. Less than 5% of all shop purchases are made with a credit/debit card.
Yes, a cup of coffee costs about USD2 to USD3 in the Philippines, but that is almost half a day's salary for most workers. A graduate engineer in the Philippines earns about USD15 per day. A shop salesperson earns about USD6.50 per 10 hour day.
Sorry mate, I wasn't aware of this. In this case if having few cups of coffee double spent would really hurt your friend salesman, you better think twice about doing it and accepting Bitcoin for such payments. It's all about that risk/reward ratio and if the risk is high for you guys than you better stay away from it.