I was looking at a clothing one where buyers order things from a site that's "yours", you get money put in your account, then you order the thing they want from another site, and get it sent to them. Clearly this is the sort of task that could never be automated .
Probably it's just you being scammed, but it's possible that this is a way to rip off people via paypal etc. Essentially, they get people's paypal account details, and steal money from their account, getting it put in your account. You transfer this money to somewhere else (ideally by Western Union or some other untraceable way), keeping a percentage. Only of course you end up having the full amount taken out of your account later, when the original theft is noriced.
The same thing can happen with bank accounts - most of the hackers are in Russia or Nigeria, and anyway, they need the ££ untraceably, so they get Brits to accept bank transfers to their bank account, and then withdraw most of the money and send it via Western Union to wherever they are. No risk for them, loads for you.