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One fascinating comment on this Register story:

Good ol' Tiscali
By Anonymous Coward
In the days of dial up I once signed up with Tiscali as they were offering a free month's trial and being a student I needed to save as much money as possible. As they wanted card details that they were saying that they were only going to start debiting after my free month and I didn't want to risk forgetting to cancel, I entered 4111 1111 1111 1111 as the card number, which is a commonly used test number that validates using the card checking algorithm. This worked and allowed me to sign up for my free month.
Surprisingly (or not) my internet access continued into month 2 .....

Reminds me of the days when Mrs U was driven mad by La Redoute accepting orders with credit card numbers that didn't even pass the checksum test. Surely it won't work anywhere any more....