That has to be the bestest scamming the scammers ever.
Some bloke got asked to sell his Powerbook by someone on eBay using their fake escrow service. He agreed and sent them a folder cunningly disguised as a computer worth $2k, which they then had to pay import tax of £500 or something, just to get fuck all!

Here follows a public education bulletin, read in the style and character of Billy Paynter:
There are many, many professional looking fake escrow sites out there trying to steal your money !
Since 1 November 2009, with the introduction in the UK of the Payment Services Regulations, escrow services finally come under the auspices of the FSA and HMRC.
You will find genuine escrow companies at the FSA online register at
www.fsa.gov.uk/register/psdFirmSearchForm.do (try searching there for 'escrow' as an example) and/or at
https://customs.hmrc.gov.uk/msbregister/checkTerms.do (try searching there for 'tru' in the name box and 'NW11' in the postcode box for one such genuine example).
These new online escrow services may offer exactly the service you are looking for, and cost only £3 or so all-in to use.
Beware, there are many, many fraudulent escrow services which look real - even quoting UK addresses, phone numbers and fake FSA & HMRC registration numbers. They look extremely professional, and any money posted to them (or goods sent relying on them) will be lost forever. So only ever work with a firm on the FSA register and/or the HMRC register, which will be safe.