John Reid, our beloved Home Secretary, wants all those nasty sex offenders to tell him their email addresses and chatroom IDs.
Can you spot the flaw in this masterful idea?
Clearly, it's going to have to be a complete list. We can't have someone just saying they're email@example.com (be interesting to see if that reaches anyone, actually) while they're also firstname.lastname@example.org in secret.
So anyone who owns a domain name and accepts email on all addresses on it is going to have a very long list.
Any combination of letters, digits, dots and dashes 'at' that domain would be valid. That's a lot. Especially as with one reading of the original RFC, there's no maximum length. Oh, and you're allowed to be case-sensitive before the 'at', so ME@ is allowed to go to a different inbox from me@.
Add in quoted addresses, where more or less anything goes, and the list becomes even more infinite.
Clearly if this is going to be printed, buy shares in paper companies now. If not, you want makers of hard disk drives.
That's before they tell them about all the IRC nicknames they could use (they're not tied to anyone), all the from: addresses, all the old email addresses they once had etc etc.