According to thisismoney.co.uk, the "robot" in question is an advanced search engine which pinpoints said rogue traders. HM Revenue & Customs (HMRC) estimates it will net £1m a year in extra VAT and "force an extra 20 businesses to register for the tax".More details over at The Register.
The figures add up thus: the National Audit Office (NAO) says VAT on ecommerce sales - which continue to rise inexorably - totalled in excess of £1bn during the 2005 to 2006 tax year. An estimated 70,000 people make a quarter of their income by trading on eBay.
UK launches VAT robot on eBay

The UK government has spend £250,000 on a web robot to hunt on high-volume eBay traders who don't pay taxes: