I got two flats yesterday: The first when my rear wheel struck a glancing blow to a small rock. A few miles later, I could feel air coming out of the tire against my ankle in regular rotations. I was just a couple of blocks to where I was going, so after my appointment I inspected and found a severe cut to the sidewall of my fairly new Vittoria tire. I booted it with the wrapper from my spare tube and made it back home.
Later in the day, I was working on a new project, installed new tires, pumped up front and rear and went off to do something else. A few minutes later I heard the unmistakable sound of air expelling from a pressurized space: the front tire was completely flat. When I pulled it, I discovered a kind of gaping hole near the valve stem (a cheap latex tube from Nashbar; same thing happened to the other one of the pair I bought).
I'm hoping I've filled my flat quota for the riding season.