I've always believed that the benefits system is to easy to fiddle. While your handing people cash to spend as they want and asking for nothing in return then it's always going to be abused.
Give them a debit card so you can see where the majority of the money is being spent and if they're long term unemployed then they should have to do something for the money. If these scumbags had to get out of bed every morning and do something productive for their hand out then it would soon have an impact.