Ah ha, I am old skool and still use a hand pump, so I've never had this issue. Mind you, I can't remember the last time I had a puncture. Alright, I'm not doing as many miles as I used to, but if you're on the road and look after your tyres (ie, inspect them for buried flints at regular intervals and always ensure they're up to pressure) you can really minimise the risk of flats. That, and ride with people who DO carry CO2.