I got my first flat on the way home. 2200 miles on the bike, most of it commute. I was going downhill at about 30 mph and the tube blew. It wasn't punctured, there was a 1.5 inch rip in the side of it right by the valve. Tire presure was 120 psi pumped up that morning. Road conditions were normal. I've gone down the hill at least 50 times on the same tube/tire.

So... just an old tube or something I could have prevented?

over pressure maybe?

or probably you ran over something, and you didn't even know about it.

which has happened to me several times

I've never seen the thing gave me a flat. If you're doing it right, you really shouldn't.

Could've just been the rim putting some pressure on the tube, and it just decided to go then. Who knows.

Heh. I'm still in the no-flat club, at least on bikes that are officially mine. Two-and-a-half months of daily riding and counting...

I got a flat but was running old cracked tires.

If you run good tubes, tires and rims, you shouldn't see to many flats unless you go off road or ride in the gutter.