As you understand fund passers are damaging the genuine business of the smart bettors (arbers, value bettors, etc). In addition, a lot of criminal activities might be hidden behind fund passing that spawns far beyond the trivial crimes of money laundering, terror funding, etc. There is a lot of bad will and no real smart betting in this technique.
Back in the days, betfair was providing master accounts whereas the sub-master account was able to open hundreds of betfair accounts.
The sub-master holder was a betting shop, either legal or illegal betting shop.
Via master accounts, betfair accounts were opened for betting shop customers.
Via those accounts you could bet either at exchanges or direct against betfair.
Once the sub-master realized how clueless the average bettor was, he usually asked betfair for a USD/CAD or even HK master account.
They did this in order to take position on the mugs bettors.
So when a customer was loosing lets say 1000 euros, the betting shop was loosing 1000USD or 1000CAD or 1000HK dollars. The betting shop was earning the currency difference. Back then, difference was from 30% for AUD to 90% for HK dollars.
Yet, there were some ''clever'' bettors.
What they tried to do was to try to pass funds from Euro accounts to USD or HK accounts.
For example, a customer was loosing lets say 1000 euros in betting shop A, his friend (or even the same guy) that had account from betting shop B was able to earn 1300USD.
Remember that in betting shop B, 1300USD equals 1300Euros, so the customer was able to earn 300 euros risk free from betting shop.
In my country this lasted till 2012. Betfair was no longer accepting customers from my country.
No idea if betfair still provide those master accounts in other countries.
If they still provide those master accounts, i wouldn't be surprised if some ''clever'' guys still wants to exploit the loophole of the system.
P.S Having that master account wasn't easy. The betting shops who didn't had the right contact in UK, they simply open 10-20 real betfair accounts in family members, relatives etc. The system there was a bit different. When a customer wanted to bet with 1000 euros, the betting shop owner was depositing 500 euros in one of his accounts. That way, he was simply taking 50% position in customer bets. Funds passing was working in the same way as before.