Well, it's happened to me - I wouldn't mind so much, except the keyboard was REALLY expensive (£75 around 18 months ago) and the letters started wearing off in the first 6 months.
Plus, I had the flu - twice (New Year's Eve I was in bed before 10.00pm) so when I got back to the computer, fuzzy brains didn't help.
So I solved it myself (can't afford a new keyboard at the moment - not at that price - and mine isn't one that's easily obtained everywhere) by using expoxy alphabet stickers and a good coat of Diamond Glaze!
- First thing to do is make sure there is no grease on the keys (I used a dishcloth wrung out in HOT soapy water, then wiped with more dishcloth rinsed in clear hot water). Make sure that keyboard is disconnected from your machine, and completely DRY before you reconnect or you could get electrocuted!
- Draw round the edge of the shape with the nozzle of the bottle, then flood with glue (make sure it's on a flat surface as this stuff acts like self-levelling concrete and you don't want it dripping inside the keyboard).
- Allow to dry overnight (it will dry clear and rock-hard).
The only downside is that I can feel the raised surface of the epoxy stickers, but am getting used to it. No letters have come off so far!