0 in the last year, since I switched to Vittoria Randonneurs (well, one tube failure, but it was a very slooooooowwww leak). The last two weeks I had Serfas Secas I got 6 flats. Before that I had a the Kendra Kontenders that my bike came with and I had two flats on those in about six months.

I'm about to tempt fate by switching out the Randonneurs for some racing tires. The Randonneurs have been amazing: Seattle's pavement is crappy as hell and I've run over glass, metal shards, ridden on a lot of gravel, and I've had no problems with around 4K miles on the set. They are heavy though, thus switching.