Surely they've learned how to handle these events by now (from Macworld):
Vodafone is struggling to activate iPad 3G Micro Sim devices due to overwheleming demand for the device.
A Vodafone call centre told us that "the server has now been down for a couple of hours" and that they cannot currently activate any Micro Sim devices bought todayOwners of iPad devices in the UK must purchase the Micro Sim separately, and three operators are offering Micro Sims alongside the iPad (Vodafone, O2, and Orange) with a fourth network, Three, selling Micro Sim cards independently.
O2 is the only service that can be activated from within the iPad itself, Orange and Vodafone customers must phone the Vodafone call centre to activate the card.
It appears that Vodafone has struggled due to the demand. The call centre is closing at 8pm today and unless it gets its system online will not be able to activate any 3G cards for iPad owners.