In principal, it is a brilliant idea. The internet has no borders so why not have a single global currency – a global marketplace that would make global e-commerce simple and easy.
In reality, they make life difficult for the user. Back in the time of Beanz, it was a solution that solved a problem for the internet companies and not the customer. Now the only reason for Facebook credits/Xbox Points is some form of lockin to the platform. Not exactly a user first approach.
People are used to their own local currency and are able to make instant value judgements on a product if it is in their own currency. Without that, there follows a delay whilst the conversion happens either in their head or worse elsewhere. That can only result in one thing – a dampening on sales.
It is important to keep things as simple as possible for the buyer.
So it is good to see both Facebook and Microsoft (rumour) take steps to change its systems to support local currencies instead. Now if only all those loyalty schemes would convert to a local currency as well..