Well, in rare cases if someone complains that they have been hacked MoneyBookers will take the money from your account in serious cases and they also sometimes shut your account down for good after 1 dispute as it has happened to someone I know who lost 300 dollars due to a scammer. But for small payments you shouldn't have any problems, I used it a lot and have had 5K GBP go though my account from various PlayerAuctions payments and the odd private sale when I use to sell Habbo. They also are a bitch about ID limitations so expect to get limited as they do it to everyone pretty much, took me 3 attempts at sending my ID in to get my account unlocked as I didn't have a scanner so had to take the picture by hand.
TL;DR - There is no dispute option, all disputes are for serious matters and are handled case by case by ringing MoneyBookers.