These days you don't see Forum Currency mod used in too many forums. 4 -5 years ago there were so many forums which used this feature. I used it in Namepros.com and dnforum.com both.
I think Namepros is the one used it for best. they has domain registration system connected to forum currency. and also the Bank was connected with Paypal so you could buy and sell currency automatically. This work great for those who could have a paypal account. There you could buy everything you need like Domains, Hosting, SEO services and designing. Also you could sell your services too.