Arbusers

There is a report of SBR

BetOnline players report being hacked07.30.2012 (01:41 PM CST)
Multiple players have reported that their BetOnline accounts have been breached. The addition of BetOnline's poker room has been a catalyst for security issues. Twelve users have reported to SBR that their accounts were broken into. In all investigated cases BetOnline has credited players with the funds that were stolen and then laundered out through the poker platform. Three recently filed disputes are still under investigation. BetOnline has also received fake claims of hacking and has been able to prove these instances to fraudsters and Sportsbook Review. These players have been added to BetOnline's blacklist which is shared among online sportsbooks. SBR advises all players to reset their password to a random combination of numbers and letters that are not used at other websites. BetOnline states they are upgrading security features while they work to identify the source of these claims.

Well..my English is not good enough to understand this news.
At the end Who is the sufferer? BetOnline or its customer?
And is BetOnline OK for arb?

It is not.
BetOnLine was reliable some years back, but not now.