One of my favourite conspiracy theories goes roughly like this: anti-virus companies would go out of business if their products were 100% effective, so they have a vested interest in keeping computers insecure. Depending on which version of the theory you subscribe to, the conspiracy means they either deliberately make insecure products, or they do the computing equivalent of black ops and actually fund the virus writers.

It’s complete cock, of course, although they’re certainly prone to exaggerating potential threats – have any of you had a virus problem on your phone, PDA or Mac? – and while Microsoft’s entry into the anti-virus market certainly looks bad (Microsoft’s responsible for the flaws, the argument goes, so if it’s got a financial interest in selling stuff to fix the flaws there’s no incentive to fix Windows), that’s equally daft: Microsoft isn’t one big monolithic corporation but a collection of individual product teams, not all of whom get on – so the people whose job it is to make Windows secure aren’t the same people involved in Microsoft security products.

That said, I am inclined to believe the age-old conspiracy theory about eBay – the one that says “eBay won’t stop scammers, because they make money from scammers”. If you sell to a scammer and lose all your cash, tough luck: eBay still expects you to pay the listing fees. If you buy tickets that never turn up, and the user’s long gone, tough luck: eBay still got the listing fees. If you get hoodwinked and pay £700 for what turns out to be a photo of a PS3 rather than a real PS3, eBay got the listing fees. If you want to take advantage of payment protection policies to reduce the risk of being screwed, you need to use PayPal – which eBay owns, and which takes a cut of each transaction. And so on.

I’m curious: as long as sufficient people use eBay to keep it in business, what incentive does it have to crack down more tightly on scams?