You can now buy a new variant of Heinz Tomato Ketchup through Facebook in the UK. You need to Like the page, then you can purchase a limited edition bottle of Balsamic Vinegar Ketchup for £1.49.
The process is pretty painful (not being able to use Paypal, having to take all the spaces out of the phone number etc), but I've bought it now 'in the interests of research'.
Update (9th June) - this has clearly worked for Heinz - the variant is now available in my local Sainsbury's:
Elsewhere, Kleenex are allowing American Facebook users to send their friends virtual and actual packets of tissues, and you can even track the spread of the giving across the states. So far one million packages have been sent. More info here.
Update - 14th March - my ketchup has arrived!