I think it's natural to be surprised if you've not come across it before and also natural to feel a little touchy and defensive if you have been affected by it. You should have seen my posts in response to a thread a while back which suggested that wetting the bed after a certain age was due to laziness on the part of the parents.
Ds1 was still in night nappies at 7. We're not talking about the odd accident - we're talking sodden nappies every single morning. He was referred to our local eneuresis clinic, had a night-time alarm, and was dry by almost 8. dilemma456, I think it's nice that your friend trusts you enough for her ds to sleep over at your house - ds1 didn't go on any sleepovers because of the bed-wetting (and I remember thinking he would have to miss his first primary residential trip in year 4 - luckily he'd cracked it in time).
People should be more open about it, I agree - because it is very common (probably at least two kids in your average class of 7 year olds).