Personalised numbers, cherished registrations, call them what you will. Vanity plates is what they are. The impulse to have your name or initials (or, even worse, something 'funny') in your car number plate is surely born out of a desire to show off slightly, to mark yourself out as 'special'. Back in the days before they were available for sale, there was something slightly awesome about a person who had tracked down a vehicle (probably and old banger), bought it, and then transferred the number to his or her own car - often a Jag, for some reason. Jimmy Tarbuck's COM1C on his Rolls was the most famous example. But now, anyone with more money than sense can have virtually anything they want on their vehicle, and the rarity value has gone. It is now merely chavvy.
Having said that, I regard it as a bit of harmless fun. One day a few years ago, when I was feeling flush, I bought a pair of plates for Anna and myself. The same single letter and low single number, and then each of our initials. They are not particularly flash, and I don't feel guilty about doing it, although I regret it now. Not so much the mild 'look-at-me' thing, as the fact that they make buying and selling a car much more expensive and bureaucratic than it needs to be. (And it makes stealth operations in a place like rural Pembrokeshire almost impossible.) I have mine back on the market, but of course in a recession a personalised plate is probably the best example you could find of 'discretionary spending'. No-one is buying.
Some can be very amusing. The local bed shop with D1VAN on their delivery vehicle is one (already posted here). Some are even impressive. If I ever saw G1NNY or DAV1D or N1GEL I would be moved to smile and tip my hat - well played, Sir or Madam. But then you get the numbers that are 'supposed' to look like letters. The local Jaguar dealer had a demonstrator with the registration B16 CAT (and a carefully-placed yellow fixing screw to make the '6' most definitely a 'G'), which was OK, but then you get into things like K3LLY or S4LLY, and the whole thing is starting to move away from reality.
Then I saw this while cruising aimlessly around eBay. I really don't get it. At. All. Click to engorge.
A great plate for an alien from the planet Tharg called J9MXA. For a human called Jemma, no. Even using all the 'rules', it still only reads 'Jgmxa'. Think he'll get £500 for it? Unlikely.